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values | evidence_publishers stringlengths 3 54 | last_reviewed stringdate 2026-09-02 00:00:00 2026-09-15 00:00:00 | reference_url stringlengths 49 81 |
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brands/amana/ptac-br-code | Amana | amana | br | light-commercial | Amana PTAC models covered by the M70 service procedure | PTC J Series; PTH J Series; Applicable Amana PTAC models in the cited manual | voltage-protection | Amana PTAC br code: low-voltage brownout protection | On the documented Amana PTAC controls, br means brownout or low-voltage protection. A brief br appearance for a few seconds while power is switched off is normal in the service flow; a continuous br display means the board sees transformer output below its threshold and requires supply, cord, transformer, accessory, an... | This reading follows the Amana PTAC service procedure cited here. Do not apply lowercase br to Amana furnaces, central equipment, or kitchen appliances; confirm the packaged terminal model and control generation. | Record whether br is momentary or continuous, photograph the voltage-model label, and note whether other equipment in the building changed simultaneously. | Receptacle, line connection, cord, transformer, 24-volt accessory, and control-board measurements require authorised PTAC service or a qualified electrician. | Do not reset a continuous br display repeatedly; its voltage path must be measured. A brief appearance only during shutdown requires no reset. | mixed-primary-sources | Amana | 2026-09-03 | https://hvac-bench.com/brands/amana/ptac-br-code/ |
brands/amana/ptac-diagnostic-codes | Amana | amana | Two-character codes | ductless-mini-split | Amana packaged terminal air conditioners and heat pumps covered by the Amana PTAC service literature | Amana PTC series; Amana PTH series; Amana DigiSmart equipped units | not-turning-on | Amana PTAC codes: two characters, and the second one matters | Amana PTAC units display short two-character codes on the front panel, and both characters carry meaning. Reading only the first, or transcribing a letter as a digit, produces a lookup that lands on an unrelated entry, which is the most avoidable error in diagnosing this equipment. | Amana PTAC equipment spans cooling-only and heat pump models with different control generations, including units fitted with the DigiSmart control system. The service literature for the model on the chassis data plate is what maps a code, and a chart written for a different generation can give a different answer. | Photograph the display close up and read both characters from the image rather than from across the room. | Check that the supply cord is fully seated and whether any protective device on the plug has operated. | Clean the filter following the owner manual and clear anything obstructing the exterior grille that can be ... | Anything that requires the chassis to come out of the wall, or a meter to touch the board, belongs to a technician on equipment of this type. | A protective device on the supply cord that operates repeatedly is a stop condition rather than something to keep resetting, and it needs an electrical assessment. | Interrupting power clears the displayed code, so photograph it first. The unit re-tests its conditions on restart, and a code that returns is reporting something that has not changed. | oem-support | Amana | 2026-09-15 | https://hvac-bench.com/brands/amana/ptac-diagnostic-codes/ |
brands/american-standard/s9v2-e21-error-code | American Standard | american-standard | E2.1 | furnace | S9V2 S-Series two-stage condensing gas furnaces | S9V2 S-Series models in installer guide 18-CE01D1-1E-EN | ignition-lockout | American Standard S9V2 E2.1 ignition retry lockout | On the documented American Standard S9V2, E2.1 means ignition retries were exceeded because flame was never sensed, followed by a one-hour lockout after three attempts. The code reports the failed ignition outcome; it does not prove whether gas delivery, ignition, grounding, flame sensing, venting, or control caused it... | This definition is restricted to S9V2 S-Series furnaces using the seven-segment integrated control display in the cited installer guide. Do not translate an older blink count or another American Standard furnace code as E2.1. | From outside closed panels, save E2.1, confirm the thermostat demand, and note sounds or factory-port observations without initiating more ignition attempts. | Gas pressure, venting, safeties, igniter, valve, burner, grounding, flame-current, and live control tests require licensed furnace service. | Do not repeatedly reset E2.1 to force more ignition attempts; preserve the lockout and arrange combustion diagnosis, especially if the code returns. | mixed-primary-sources | American Standard | 2026-09-03 | https://hvac-bench.com/brands/american-standard/s9v2-e21-error-code/ |
brands/american-standard/furnace-fault-history-record | American Standard | american-standard | Stored fault history | furnace | American Standard gas furnaces whose integrated controls retain a stored fault history alongside the current status | S9V2 series; Platinum series furnaces; Gold series furnaces | communication-fault | American Standard fault history: the record outlasts the symptom | An American Standard furnace control keeps a record of previous faults as well as reporting the current one, and that record survives the power interruptions people perform while troubleshooting. Where a fault is intermittent, the stored history is the only evidence that survives long enough to be diagnosed. | Fault history retention, and the method of retrieving it, differ between American Standard control platforms and between communicating and conventional systems. The service facts document for the exact furnace is the reference for how the history is read and how many entries are retained. | Photograph the diagnostic indication before interrupting power, even when you intend to reset the furnace afterwards. | Keep a dated note of each occasion heating has failed and how long it was unavailable. | Ask explicitly for the stored fault history to be retrieved during any service visit for an intermittent compla... | Retrieving stored history requires access to the control and, on some platforms, a specific button sequence or service tool, which is a technician task. | Any entry concerning a limit, a rollout, or combustion is a stop condition regardless of the fact that heating has since resumed. | Interrupting power clears what is displayed and leaves the stored record intact, so a reset costs you the immediate code and nothing more. Photograph before resetting and the cost is nothing at all. | mixed-primary-sources | American Standard; Trane | 2026-09-15 | https://hvac-bench.com/brands/american-standard/furnace-fault-history-record/ |
brands/ariston/clas-overheat-fault-codes | Ariston | ariston | 1-series | boiler | Ariston Clas gas boilers whose fault codes are grouped by leading digit in the Ariston user documentation | Clas ONE; Clas ONE System; Clas Premium Evo; Clas HE | overheat-lockout | Ariston Clas overheat codes: the 1-series group and what it points at | Ariston organises Clas fault codes into groups by their leading digit, and the 1-series belongs to the primary water circuit. An overheat entry within that group therefore comes pre-labelled as a water-side condition, which is a genuinely useful piece of structure that most manufacturers do not offer. | The grouping described here is the one Ariston uses in Clas user documentation. Ariston sells other ranges with their own conventions, and appliances sold under related brand names are documented separately. Match the code to the manual issued with your own boiler before applying the grouping. | Record all three digits of the code exactly, since the leading digit and the pair that follow it do different jobs. | Read the system pressure gauge while the system is cold and write the figure down. | Feel each radiator after a heating attempt and map which heat, which do not, and where the cold begins on the panel. | Anything that restores flow through a sealed heating circuit, from a new circulator to a chemical clean, is Gas Safe registered work when it involves the appliance itself. | A boiler making boiling or knocking sounds should be left off rather than run while waiting, because those episodes deposit scale on the exchanger... | Ariston appliances allow a reset from the control panel. One attempt establishes whether the condition repeats; further attempts heat the exchanger under the same restricted flow that caused the trip. | mixed-primary-sources | Ariston | 2026-09-15 | https://hvac-bench.com/brands/ariston/clas-overheat-fault-codes/ |
brands/ariston/clas-one-108-refill | Ariston | ariston | 108 | boiler | Ariston Clas ONE, Clas System ONE, and Alteas ONE boilers showing 108 | Clas ONE; Clas System ONE; Alteas ONE; Clas HE Evo | low-water-pressure | Ariston 108 error code: refill request for low system pressure | Ariston shows 108 when the heating circuit pressure has fallen below the level the boiler needs, and it is asking for a refill. The owner opens the filling taps under the boiler until the gauge reads 1.0 to 1.5 bar cold, closes them, then clears the code with the reset control. A drop again within days points at a leak... | This applies to Ariston Clas and Alteas family boilers whose user documentation lists 108 as a filling request. Ariston uses separate codes for a faulty pressure transducer, so if the gauge is already in band and 108 stays, treat it as a sensor branch and call an engineer. | With the boiler cold, open both filling taps under the boiler slowly until the gauge reads 1.0 to 1.5 bar, then turn both taps fully off and press reset once. | Note whether 108 clears after the reset and whether the pressure is still in band the next morning. | A pressure that will not hold, 108 showing with the gauge already in band, a suspected transducer fault, or any check inside the boiler casing needs a Gas Safe registered engineer. | Press reset once after a correct refill to 1.0 to 1.5 bar. If 108 returns straight away, do not keep resetting; the reading is still low or a sensor fault is present. | mixed-primary-sources | Ariston | 2026-09-09 | https://hvac-bench.com/brands/ariston/clas-one-108-refill/ |
brands/ariston/clas-one-error-501 | Ariston | ariston | 501 | boiler | Clas One and Clas System One condensing gas boilers | Clas One 24; Clas One 30; Clas One 38; Clas System One models in the cited user literature | no-flame-lockout | Ariston Clas One error 501: no flame detected | On the documented Ariston Clas One family, error 501 is a non-volatile lockout because flame was not detected. The boiler does not restart automatically and the user manual permits reset-button attempts, capped at five within 15 minutes. A returning 501 requires authorised technical service, not continued resetting. | This definition applies to Clas One and Clas System One user literature linked by Ariston. Nimbus heat pumps, Nuos water heaters, other One-series generations, and regional gas configurations need their own manual. | Photograph 501 and the model, check whether other gas appliances operate, and observe sounds only from outside the sealed case. | Gas supply pressure, valve, ignition, burner, flame signal, electrode, grounding, flue, condensate, control, and sealed-case work require authorised qualified service. | Use a single observed reset rather than aiming for the five-in-15-minute maximum; stop when 501 returns and request service. | mixed-primary-sources | Ariston | 2026-09-03 | https://hvac-bench.com/brands/ariston/clas-one-error-501/ |
brands/baxi/e110-overheat-lockout | Baxi | baxi | E110 | boiler | Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material | Baxi 800 combi; Baxi 600 combi; Baxi Duo-tec; Baxi Platinum | overheat-lockout | Baxi E110: the overheat lockout that is really a circulation message | Baxi uses E110 for an overheat condition, where the boiler has exceeded its permitted maximum temperature or the safety thermostat has tripped. The measurement is genuine, but heat only accumulates when something stops carrying it away, so the investigation belongs to the water side of the system more often than to the... | Baxi publishes E-series codes across several domestic ranges, and the detail behind a number can differ between them. The list on the label behind the casing flap of your own appliance governs, and a Potterton or Main boiler from the same group carries its own published list even where components are shared. | Check the system pressure gauge on the boiler and write down the reading while the system is cold. | Feel every radiator after a heating attempt and record which warm up, which stay cold, and where on the panel the cold begins. | Note any noise from the boiler and whether it coincides with firing, and stop using the he... | Pump testing and replacement, venting a sealed primary circuit, cleaning or flushing a system, and resetting a tripped safety thermostat are Gas Safe registered tasks. | A boiler that boils audibly should not be run while waiting for an appointment, because each episode damages the heat exchanger surface further. | Baxi permits a reset from the control panel, and one attempt establishes whether the lockout repeats. Repeating it against unchanged circulation subjects the exchanger to the same overheating each time. | oem-support | Baxi | 2026-09-15 | https://hvac-bench.com/brands/baxi/e110-overheat-lockout/ |
brands/baxi/e119-low-pressure | Baxi | baxi | E119 | boiler | Baxi and Potterton domestic boilers that display E119 | Baxi 600; Baxi 800; Baxi Platinum; Potterton boilers sharing the E119 code | low-water-pressure | Baxi E119 fault code: low system pressure and how to clear it | Baxi assigns E119 to low water pressure in the heating system, below the level the boiler needs to operate. It is cleared by repressurising to between 1 and 1.5 bar with the filling device fitted to the boiler, and it points to a leak only if the pressure will not stay up afterwards. | This covers Baxi and Potterton boilers whose published fault guidance lists E119. Baxi uses E118 for a related low-pressure condition on some models, so match the exact digits, and confirm the boiler model before choosing a filling method. | With the boiler off, read the gauge and, if it is low, admit water with the boiler filling device until it reads 1 to 1.5 bar cold, then close the device fully. | Keep a short note of each repressurise, the date, and the pressure before and after, so a repeat loss can be measured. | A pressure that will not hold, visible damp or staining, a dripping outside overflow pipe, or any expansion vessel or internal check needs a Gas Safe registered engineer. | The boiler should clear E119 on its own once the pressure is back in band. Do not keep repressurising when it will not hold, because repeated refilling introduces oxygen into the system. | oem-support | Baxi | 2026-09-09 | https://hvac-bench.com/brands/baxi/e119-low-pressure/ |
brands/baxi/e133-fault-code | Baxi | baxi | E133 | boiler | Baxi domestic boilers covered by the manufacturer E133 guidance | Baxi 600; Baxi 800; Baxi Platinum models listed in applicable documentation | ignition-lockout | Baxi E133: failed ignition and the frozen-condensate clue | Baxi defines E133 as a failed ignition condition. In freezing weather, a blocked frozen condensate pipe can contribute on installations with an external condensate run, but E133 is not a frozen-pipe detector. Fuel supply, ignition, flame proof, condensate, venting, and controls remain professional diagnostic branches. | This guidance applies only to Baxi boilers whose own user or service instructions list E133. Product generation, country, and fuel setup matter; confirm the complete model before using any reset or thawing instruction. | Confirm the full model and weather, check other gas appliances, and inspect only an easily accessible ground-level external condensate section. | Inaccessible or internal condensate, recurring freezing, gas supply, ignition, electrode, combustion, vent, flame-proof, and sealed-case work require Gas Safe service. | Use one reset only as the exact Baxi user manual permits; do not repeat it when E133 remains or returns after any safe condensate action. | oem-support | Baxi | 2026-09-03 | https://hvac-bench.com/brands/baxi/e133-fault-code/ |
brands/baxi/e160-fan-fault | Baxi | baxi | E160 | boiler | Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material | Baxi 800 combi; Baxi 600 combi; Baxi Duo-tec; Baxi EcoBlue | fan-fault | Baxi E160: fan or fan wiring, and why the boiler will not compromise | Baxi publishes E160 as a fan or fan wiring fault. Two distinct situations sit inside that phrase: a fan that is not turning at all, and a fan that is turning but whose speed the control cannot confirm. Both stop the boiler, and telling them apart from outside the casing starts with whether you can hear anything. | The E-series codes are published by Baxi across several domestic ranges, and the same number does not necessarily carry the same detail on every one. Read it against the list on the label behind your own casing flap, and treat lists compiled for other manufacturers as unrelated. | Stand near the boiler during one start attempt and note whether any fan sound occurs, and for how long. | Write the code down exactly, since Baxi E-series numbers are three digits and adjacent numbers mean different things. | Think back over the last few months for anyone who has worked on the appliance or the circuits... | Fan testing, wiring inspection, and fan replacement on a room-sealed gas appliance are Gas Safe registered tasks in the United Kingdom. | Leave the front of the appliance exactly as it is. That panel is part of the sealed enclosure separating combustion from room air, and it is not an inspection hatch. | A reset permits one further attempt, and the fan check happens within seconds of it. Where the fan cannot run or cannot be accepted, additional resets produce the same outcome without adding information. | oem-support | Baxi | 2026-09-15 | https://hvac-bench.com/brands/baxi/e160-fan-fault/ |
brands/blueridge/bmkh-code-groups | Blueridge | blueridge | BMKH code groups | ductless-mini-split | Blueridge BMKH ductless mini-split systems documented in the Blueridge manual library | BMKH wall-mounted indoor units; BMKH floor console indoor units; BMKH multi-zone systems | communication-fault | Blueridge BMKH codes: a distributor brand with real documentation | Blueridge publishes documentation per indoor unit style as well as per series, so a wall-mounted BMKH and a floor console BMKH carry different manuals. Reaching for the right one matters because indoor-side entries relate to hardware that differs between those styles even within the same model family. | Blueridge is a distributor brand whose equipment is documented under its own manuals rather than under the manufacturer that builds it. Those manuals are the reference, and documentation for visually similar equipment sold under another name is not a substitute. | Identify the indoor unit style and find the manual issued for that style rather than for the series in general. | Photograph the displayed code and both model numbers before interrupting power. | Switch to fan mode if condensate is visible, so the coil stops producing water while the fault is outstanding. | Condensate pumps, sensing elements, and fan assemblies sit inside indoor casings that also carry the supply, which makes access qualified work. | Conditions raised by the outdoor unit involve the refrigerant circuit and the drive, and both require certification to work on. | Cutting the supply once will show whether the report was latched or whether the condition is still live. Where condensate is involved, resist restarting in cooling afterwards, since every cycle sends more water into a path that has already fallen behind. | mixed-primary-sources | Alpine Home Air; Blueridge | 2026-09-15 | https://hvac-bench.com/brands/blueridge/bmkh-code-groups/ |
brands/blueridge/bmkh-e1-error-code | Blueridge | blueridge | E1 | ductless-mini-split | BMKH floor-ceiling indoor units | BMKH floor-ceiling units covered by the December 2023 manual | high-pressure-protection | Blueridge BMKH E1: compressor high pressure protection | Blueridge assigns E1 on this range to compressor high pressure protection. The control has stopped the compressor because pressure on the high side reached a limit, which is a protective action rather than a component failure. | This meaning comes from the code table in the Blueridge BMKH floor-ceiling manual dated December 2023. Blueridge publishes different tables for its other indoor styles, and E1 on another manufacturer's ductless equipment routinely means something unrelated, so match the model plate before using this page. | Record whether the code appeared in cooling or in heating, and the outdoor conditions at the time. | Clear stored items, planting, and debris away from the outdoor cabinet so air can reach and leave the coil. | Check the indoor filter and the space in front of the unit, and confirm the fan is not left on its lowest set... | Pressure measurement requires gauges on service ports and belongs to a certified technician. | Do not restart repeatedly against a protection code, because each attempt drives the system back toward the limit that stopped it. | Clearing a restriction and trying again is a legitimate test and worth doing once. Cycling the supply to clear the display without changing anything else repeats the condition rather than resolving it. | mixed-primary-sources | Blueridge; Alpine Home Air | 2026-09-03 | https://hvac-bench.com/brands/blueridge/bmkh-e1-error-code/ |
brands/bosch/climate-5000-ec07-error | Bosch | bosch | EC 07 | ductless-mini-split | Climate 5000 Generation 3 R-454B multi-zone | Climate 5000 Gen 3 R-454B multi-zone outdoor units in the May 2025 service manual | outdoor-fan-speed-fault | Bosch Climate 5000 EC 07 outdoor fan speed fault | On Bosch Climate 5000 Generation 3 R-454B multi-zone equipment, EC 07 means the outdoor fan speed is outside the control's expected range. The service procedure considers fan obstruction and assembly, motor wiring and feedback, the motor itself, and the outdoor PCB; the code does not select one of them. | This code definition applies only to the May 2025 Climate 5000 Gen 3 R-454B multi-zone manual. Earlier R-410A Climate 5000, single-zone, IDS, boiler, and Compress products use different references. | With the unit off, document EC 07, the exact outdoor model, guard and clearance condition, ice, and fan behavior from outside the cabinet. | Fan access, motor resistance and feedback, harness, live inverter-board, refrigerant, and R-454B safety checks require qualified Bosch service. | One model-approved restart can show whether EC 07 persists; do not repeatedly energise a fan that is stalled, rubbing, iced, or faulting. | mixed-primary-sources | Bosch Home Comfort | 2026-09-03 | https://hvac-bench.com/brands/bosch/climate-5000-ec07-error/ |
brands/bosch/climate-5000-pc30-pc31 | Bosch | bosch | PC 30 / PC 31 | multi-zone | Climate 5000 Generation 3 R-454B multi-zone outdoor units | M4OB-36HFN8-Q; M5OD-42HFN8-Q; M5OE-42HFN8-Q | pressure-protection | Bosch PC 30 and PC 31: codes that exist on three outdoor models | PC 30 is high pressure protection and PC 31 is low pressure protection, and the service manual restricts both to three named outdoor units. An outdoor unit outside that list has no pressure switches to report on and will show a different code instead. | The code table here is from the Bosch Climate 5000 Generation 3 R-454B multi-zone service manual dated May 2025, which covers the outdoor units. Indoor codes are published in the indoor service manual, and earlier Climate 5000 generations on a different refrigerant platform have their own documentation. | Record the full outdoor model number from the data plate and check it against the three models these codes are published for. | Photograph the code exactly, since the prefix and the final character both change the meaning. | Note the outdoor temperature, the mode, and how long the system had been running when it stoppe... | Pressure measurement requires gauges on service ports and a certified technician, and this refrigerant platform has its own handling requirements. | Do not restart repeatedly against a protection code, since each attempt returns the system to the condition that stopped it. | Clearing an obstruction and trying again is a reasonable single test. A protection that returns without any change to the conditions is reporting the same limit, and further restarts do not move it. | mixed-primary-sources | Bosch Home Comfort | 2026-09-03 | https://hvac-bench.com/brands/bosch/climate-5000-pc30-pc31/ |
brands/bosch/climate-5000-code-structure | Bosch | bosch | Prefix and digits | ductless-mini-split | Bosch Climate 5000 ductless mini-split systems documented in the Bosch service and manual library | Climate 5000 single-zone; Climate 5000 multi-zone indoor units; Climate 5000 outdoor units | communication-fault | Bosch Climate 5000: reading a code that names an indoor or outdoor origin | Bosch Climate 5000 codes are built from a prefix and a pair of digits, and the prefix carries real information: it says whether the indoor unit, the outdoor unit, or the link between them raised the condition. Reading the prefix first narrows a search that would otherwise begin with the digits and end in the wrong tabl... | The Climate 5000 name covers single-zone and multi-zone equipment across more than one generation, and code assignments differ between them. Match the prefix and digits against the manual for the indoor and outdoor models on your data plates rather than against a chart for the range as a whole. | Photograph the indoor display so that the prefix and the digits are both captured together. | Copy the indoor and outdoor model numbers from their data plates before searching anything. | List any building work, decorating, or trades activity near the pipework or its cable route in recent months. | Interconnecting cable on this equipment carries mains voltage between the units, so inspecting, testing, or reterminating it is qualified work. | Outdoor protections reported through the indoor display involve the refrigerant circuit, which is certified activity rather than an owner check. | Power interruption clears the display and the system rebuilds its communication on restart, which makes one restart a genuine test. Capture the full code first, because the display is the only place it appears. | mixed-primary-sources | Bosch Home Comfort | 2026-09-15 | https://hvac-bench.com/brands/bosch/climate-5000-code-structure/ |
brands/bryant/evolution-communication-loss | Bryant | bryant | Communication loss | controls-thermostats | Bryant Evolution communicating systems using the Evolution Connex control and a four-conductor communication bus | Evolution Connex control; Evolution communicating gas furnaces; Evolution communicating heat pumps and air conditioners | communication-fault | Bryant Evolution communication loss: when the system stops talking to itself | A Bryant Evolution system is not a thermostat with switched wires. The control, the indoor unit, and the outdoor unit exchange data over a shared bus, and losing that conversation stops coordinated operation even when every individual component is healthy. A communication message therefore points at the path between de... | This describes the communicating architecture Bryant uses for Evolution systems. A Bryant system with a conventional thermostat and individually switched conductors does not behave this way, and the Carrier equivalent of the same architecture carries its own message set. Confirm you have a communicating control before ... | Write down the exact message the wall control shows, including any number or reference it displays alongside it. | Establish whether heating or cooling still happens at all, and whether output varies or sits at one fixed level. | Note any recent storms, flooding, landscaping, or building work near the outdoor unit or t... | Testing a communication bus, inspecting outdoor terminal blocks, and replacing damaged interconnecting cable are tasks inside enclosures carrying line voltage. | Do not substitute a conventional thermostat for a communicating control to restore operation. The equipment expects data on those conductors, not switched vol... | Restoring power re-establishes the conversation if the path is intact, so a message that clears and returns is describing a connection that is marginal rather than one that has been repaired. | mixed-primary-sources | Bryant | 2026-09-15 | https://hvac-bench.com/brands/bryant/evolution-communication-loss/ |
brands/carrier/furnace-status-code-13-limit-lockout | Carrier | carrier | 13 | furnace | Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, as covered by troubleshooting guide 58-3T | Deluxe two-stage induced-combustion furnaces with PSC blower; Deluxe two-stage induced-combustion furnaces with ICM blower | limit-circuit-lockout | Carrier status code 13: the lockout that follows a limit or rollout switch | Carrier lists status code 13 as a limit or flame rollout switch lockout. The control had already seen that circuit open, reported it, and then decided the condition had lasted long enough to stop trying. A lockout is a deliberate refusal to restart, so code 13 is a stronger statement than the open-circuit code that pre... | This reading is taken from Carrier troubleshooting guide 58-3T, which covers deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors. Other Carrier furnace controls, and the same numbers on Bryant or Payne equipment, are read from their own literature. Confirm the model on the furnace ratin... | With the furnace switched off, inspect the return-air filter and fit a clean one of the specified size and type if it is loaded. | Walk the house and confirm that supply registers and return grilles are open and not covered by furniture, rugs, or stored items. | Record the flash pattern through the sight glass without ... | Identifying which safety device opened, measuring temperature rise, and inspecting combustion and venting are licensed gas-furnace tasks. | Treat soot, scorching, an odour of combustion products, or a carbon monoxide alarm as an immediate stop. Get fresh air into the space, keep the appliance off, and use the emergency... | Carrier's control clears a lockout on its own after a fixed interval, so an automatic retry proves nothing about the underlying condition. Interrupting power to force an earlier retry removes the record without changing the circuit. | mixed-primary-sources | Carrier | 2026-09-15 | https://hvac-bench.com/brands/carrier/furnace-status-code-13-limit-lockout/ |
brands/carrier/furnace-status-code-14-ignition-lockout | Carrier | carrier | 14 | furnace | Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, covered by troubleshooting guide 58-3T | Deluxe two-stage induced-combustion furnaces, PSC blower; Deluxe two-stage induced-combustion furnaces, ICM blower | ignition-lockout | Carrier status code 14: ignition lockout after four failed trials | Status code 14 on this Carrier control is ignition lockout. The guide states that lockout occurs after four consecutive unsuccessful trials for ignition and that the control resets itself automatically after three hours. The number 14 therefore counts failures; it does not identify which part of the ignition sequence f... | The count of four trials and the three-hour automatic reset are stated in Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Single-stage and modulating Carrier controls, and the same number on other manufacturers, follow their own literature and their own retry counts. | Confirm that other gas appliances in the property are working normally, which separates a supply-wide interruption from a furnace-specific fault. | Check that the thermostat is calling for heat and that its batteries, if fitted, are good, so a failed call is not mistaken for a failed ignition. | Note the time of each l... | Measuring gas pressure, testing igniter resistance, cleaning or replacing a flame sensor, and inspecting venting are licensed gas-furnace tasks. | A smell of gas at any point is an emergency. Leave the property, avoid switches and flames, and contact the emergency number for your gas supplier before anything else. | Carrier's control releases this lockout automatically after three hours. Cutting power to force an earlier retry only spends four more trials against the same condition and erases the diagnostic record. | oem-service-manual | Carrier | 2026-09-15 | https://hvac-bench.com/brands/carrier/furnace-status-code-14-ignition-lockout/ |
brands/carrier/infinity-code-16-with-53-55-47 | Carrier | carrier | 16 | ducted-split | Carrier Infinity System Control paired with communicating equipment, with the outdoor-unit code structure documented for 24VNA6 and 25VNA4 variable-speed units | Carrier 24VNA6 variable-speed heat pump; Carrier 25VNA4 variable-speed air conditioner; Carrier Infinity System Control SYSTXCCITC | communication-fault | Carrier Infinity code 16 with 53, 55 or 47: telling a communication fault from a failed sensor | Read the number as a pair before deciding anything. On 24VNA6 and 25VNA4 equipment the outdoor board reports a base code plus an expansion code, so 16, 53 and 55 occupy different columns of one table and carry different meanings depending on the column they came from. A genuine loss of communication with the Infinity S... | The code structure described here is the one published for the 24VNA6 and 25VNA4 outdoor units. Carrier furnaces, fan coils and older Infinity outdoor sections keep their own tables, and a two-digit number copied from one of those is not evidence about a variable-speed unit carrying this board. | Photograph the wall control message, the outdoor display, and the state of the Comm light before any power is interrupted. | Write down whether the number appeared in a code position or in a temperature field on a status screen. | Note which modes the system still accepts, because a mode that runs is evidence about wha... | Resistance measurement at the control board connector, and any inspection inside the outdoor cabinet, is qualified service work. | Tracing the communication path between the outdoor board and the Infinity System Control involves energised low-voltage wiring and belongs to a technician. | Interrupting power clears the display and can discard the sequence that explains the fault, so capture every screen first. Repeated restarts are not a repair for either condition described here. | mixed-primary-sources | Carrier | 2026-09-04 | https://hvac-bench.com/brands/carrier/infinity-code-16-with-53-55-47/ |
brands/carrier/furnace-status-code-24-fuse-open | Carrier | carrier | 24 | furnace | Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T | Deluxe two-stage induced-combustion furnaces with PSC blower motors; Deluxe two-stage induced-combustion furnaces with ICM blower motors | control-power-fault | Carrier status code 24: the secondary voltage fuse is open | Carrier defines status code 24 as the secondary voltage fuse being open. That fuse protects the 24-volt control circuit, and the guide specifies a 3 amp automotive blade type that must be replaced only with another 3 amp fuse. A fuse opens because something drew more current than the circuit allows, so the fuse is the ... | The fuse rating and the code definition come from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Fuse ratings differ between control platforms, and fitting anything other than the rating in the literature for your exact model removes the protection the circuit was designed around. | Establish exactly what has stopped: heating alone, heating and cooling together, or any accessory such as a humidifier. | Check whether the thermostat display is blank or still powered, since that alone tells the technician which side of the circuit lost supply. | Write down any recent work on thermostats, cabling, out... | Locating a short in the 24-volt circuit, testing the transformer, and replacing the control fuse are tasks inside an enclosure that also carries line voltage, so they belong to a qualified technician. | Never fit a fuse of a higher rating than the literature specifies. The protection the original rating provides is the... | There is nothing to reset here. The circuit stays open until the fuse is replaced, and replacing it without finding the short simply repeats the event. | mixed-primary-sources | Carrier | 2026-09-15 | https://hvac-bench.com/brands/carrier/furnace-status-code-24-fuse-open/ |
brands/carrier/furnace-status-code-31 | Carrier | carrier | 31 | furnace | Carrier two-stage and variable-speed modulating condensing furnaces that report status code 31 | 58MVC; 58MVP; 59MN7A; Infinity 98 gas furnace | pressure-switch-fault | Carrier furnace status code 31: pressure switch did not close | Carrier assigns status code 31 to a high-heat pressure switch input that did not close when the control called for high or intermediate heat, or that opened during the heat cycle. It reports the state of a proving circuit, so the draft inducer, venting, condensate, tubing, wiring, and the switch itself all stay on the ... | This reading follows Carrier service literature for two-stage and modulating condensing furnaces that flash a two-digit status code. Single-stage models and other code numbers behave differently, and the legend printed inside the furnace door is what confirms the meaning for a given board. | With the furnace off, clear any frost, ice, snow, or debris from the outdoor vent and intake terminations and confirm the terminations are not obstructed. | Check the furnace filter is clean, the return and supply grilles are open, and the furnace access door is fully closed. | Measuring inducer pressure, testing the switch and inducer, clearing the condensate trap, and any wiring or gas-valve work require a qualified heating technician, and the pressure switch must never be bypassed. | A single power cycle to clear the code is reasonable after checking the terminations and filter. If status code 31 returns on the next call for high heat, leave the furnace off for service. | oem-service-manual | Carrier | 2026-09-09 | https://hvac-bench.com/brands/carrier/furnace-status-code-31/ |
brands/carrier/furnace-status-code-32-pressure-switch | Carrier | carrier | 32 | furnace | Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T | Deluxe two-stage induced-combustion upflow furnaces; Deluxe two-stage induced-combustion downflow furnaces; Deluxe two-stage induced-combustion horizontal furnaces | pressure-switch-fault | Carrier status code 32: three switches share one number | Carrier writes status code 32 as the low-heat pressure switch, the draft safeguard switch, or the downflow auxiliary limit switch failing to close or reopening after it had closed. Three separate devices share the entry, and the control cannot tell you which one acted, so the code narrows the fault to a group rather th... | Guide 58-3T is the source here, and it covers deluxe two-stage induced-combustion equipment only. The auxiliary limit named in the entry is present on downflow arrangements, so what the code can mean depends on how your furnace is installed as well as on which model it is. | Look at the outdoor vent and intake terminations from ground level and note any ice, snow, nesting material, or vegetation without attempting to clear anything at height. | Time how long the furnace produces heat before it stops, and whether the burners lit at all. | Keep a short log of the outdoor temperature and wind... | Measuring draft pressure, inspecting the vent system, clearing condensate traps, and testing pressure switches are licensed gas-furnace tasks. | Combustion products detected indoors, or a carbon monoxide alarm sounding, outranks every other instruction on this page. Get people out, open up the space, and call the emerg... | Interrupting power clears the display, and the control then re-tests the same circuit at the next call for heat. Where a draft safeguard may be involved, repeated retries are the wrong response regardless of whether they appear to work. | oem-service-manual | Carrier | 2026-09-15 | https://hvac-bench.com/brands/carrier/furnace-status-code-32-pressure-switch/ |
brands/carrier/58mcb-code-33-limit-circuit-fault | Carrier | carrier | 33 | furnace | Carrier 58MCB Series 110 and 120 condensing gas furnaces | 58MCB040; 58MCB060; 58MCB080; 58MCB100; 58MCB120 | limit-circuit-fault | Carrier 58MCB code 33: limit circuit fault is two different warnings | Carrier 58MCB status code 33 means the limit circuit is open. That circuit includes the high-limit switch and flame-rollout switches, so the code does not tell you which safety opened. Check only the filter and unobstructed grilles; visible flame rollout, soot, a gas odor, or a returning code requires immediate service... | This interpretation is limited to the Carrier 58MCB Series 110 and 120 manual. Other Carrier furnace controls can use the same number with different timing or component groupings, so confirm the model on the furnace rating plate. | With the furnace off, inspect only the normal homeowner-access filter and replace it with the specified size and type if loaded. | Confirm return grilles and supply registers are open and clear without reaching into ducts or removing furnace panels. | Record the full flash pattern, operating sequence, and any later cod... | Identifying the open device, measuring temperature rise, testing safeties, and inspecting combustion require licensed gas-furnace service. | A rollout indication, soot, gas odor, or carbon-monoxide alarm is a stop condition, not a reset opportunity. | Do not repeatedly reset code 33. A returning open safety circuit needs its temperature or combustion cause identified before the furnace runs again. | mixed-primary-sources | Carrier | 2026-09-09 | https://hvac-bench.com/brands/carrier/58mcb-code-33-limit-circuit-fault/ |
brands/carrier/furnace-status-code-34-ignition-proving | Carrier | carrier | 34 | furnace | Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T | Deluxe two-stage induced-combustion furnaces, natural gas; Deluxe two-stage induced-combustion furnaces, propane | ignition-lockout | Carrier status code 34: ignition proving failed on this trial | Carrier lists status code 34 as an ignition-proving fault. It records that a trial for ignition did not end with a proven flame, and unlike code 14 it does not mean the control has given up. Seeing 34 without 14 means the furnace is still retrying, which is the moment when observing what happens is worth most. | Read here from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. The relationship between the per-trial fault and the lockout that follows it is specific to this control family, and other manufacturers using the number 34 are not describing the same thing. | Listen to a full heating cycle from a safe distance and note whether a flame is established at all, and whether it is lost after establishing. | Keep a tally over several days of how many heat calls succeed and how many fail, with the times of day. | Confirm that other gas appliances behave normally and note whether fa... | Measuring the flame signal, testing igniter resistance, cleaning a sensing electrode, and checking manifold gas pressure are licensed gas-furnace tasks. | Any smell of gas requires the emergency response for your supplier before any further troubleshooting: leave the property, avoid switches, and call from outside. | Code 34 is a per-trial record rather than a latched state, so the furnace continues retrying without intervention. Clearing it by interrupting power removes the history that shows how the fault is progressing. | mixed-primary-sources | Carrier | 2026-09-15 | https://hvac-bench.com/brands/carrier/furnace-status-code-34-ignition-proving/ |
brands/cooper-and-hunter/sophia-cassette-e1-error | Cooper & Hunter | cooper-and-hunter | E1 | ductless-mini-split | Sophia multi-zone cassette indoor units | Sophia cassette indoor units covered by the cited owner's manual | communication-fault | Cooper & Hunter Sophia cassette E1 communication error | For the documented Cooper & Hunter Sophia multi-zone cassette, E1 means the indoor and outdoor equipment are not communicating. It describes the failed control path, not a confirmed outdoor board failure; field wiring, terminals, pairing, supply, and both control ends still need to be proved. | This page applies only to the Sophia multi-zone cassette manual cited below. Cooper & Hunter sells several platforms whose identical E1 display can mean something else, so identify the series and indoor-unit style first. | Record the code, paired model numbers, whether the cassette ever worked, and the operating status of every other zone without removing covers. | Addressing, terminal, continuity, voltage, communication-signal, and board checks require an installer qualified for the Sophia multi-zone platform. | Use one restart only if the Sophia instructions permit it; do not repeatedly clear a communication code that immediately returns. | mixed-primary-sources | Cooper and Hunter | 2026-09-03 | https://hvac-bench.com/brands/cooper-and-hunter/sophia-cassette-e1-error/ |
brands/cooper-and-hunter/f-series-sensing-codes | Cooper & Hunter | cooper-and-hunter | F-series | ductless-mini-split | Cooper and Hunter ductless mini-split systems documented in the Cooper and Hunter support library | Sophia series; Astoria series; Olivia series; Mia series | temperature-sensor-fault | Cooper and Hunter F codes: a sensing family shared across the range | Cooper and Hunter groups its sensing faults into an F-series, where the letter marks a temperature sensing problem and the digit identifies which sensor position the control was reading. Every entry in the family shares the same meaning at the level of the letter: a reading the control will not act on. | Cooper and Hunter sells several ductless ranges and publishes documentation per range rather than as one list. The digit following the F identifies a sensor position within the model's own scheme, so the support document for your series is what maps it. Ranges from other suppliers using similar lettering are unrelated. | Photograph the display showing the complete code, letter and digit together, before power is interrupted. | Compare the temperature the indoor unit reports against a separate thermometer and note both figures. | Record which indoor unit is affected and whether any others on the system are behaving oddly. | Sensing elements, their connectors, and the harnesses linking them to the board sit inside casings that also carry mains supply, so access is qualified work. | An outdoor sensing fault can accompany water ingress into the enclosure, which needs assessing beyond the sensing element itself. | The reading is taken again on the next start, so a code that returns immediately is describing an unchanged resistance. Capture the code before interrupting power, since the display is where it lives. | mixed-primary-sources | Cooper and Hunter | 2026-09-15 | https://hvac-bench.com/brands/cooper-and-hunter/f-series-sensing-codes/ |
brands/daikin/a3-drain-level-control | Daikin | daikin | A3 | ductless-mini-split | Daikin indoor units covered by the SM-TS3 malfunction code chart, spanning room air, SkyAir, and VRV indoor equipment | FXFQ series cassettes; FXMQ series ducted; FXSQ series ducted; FXZQ series cassettes | water-leak | Daikin A3: drain level control abnormality on the indoor unit | Daikin assigns A3 to the drain level control system in the indoor unit division of its malfunction chart. The control detected that the condensate level or the drain system response was outside normal, and it stopped operation to prevent the tray overflowing. The chart names the system, which is why A3 covers the float... | A3 is read from the Daikin After Sales Service malfunction code chart, which divides codes by unit rather than by model. The chart gives the meaning of the letter and detail code; the component layout behind it comes from the service manual for the specific indoor unit. A wall-mounted room air unit without a drain pump... | Select fan operation or switch the affected indoor unit off so the coil stops condensing while the fault is outstanding. | Record the unit number shown beside A3 and the room that unit serves, which identifies the address for service. | Check whether the external condensate discharge point produced any water during the... | Opening a cassette decoration panel, testing a float switch, or clearing a drain pan inside the indoor unit is qualified service work on this equipment. | Any water that has reached ceiling material, lighting, or an electrical accessory is a stop condition, and the indoor unit should be isolated rather than restarted. | Clearing the display resets the report, not the level. One restart may confirm the fault repeats; further restarts add condensate to a tray the system has already declared it cannot empty. | mixed-primary-sources | Daikin Industries | 2026-09-15 | https://hvac-bench.com/brands/daikin/a3-drain-level-control/ |
brands/daikin/a5-error-code | Daikin | daikin | A5 | ductless-mini-split | Daikin 15 and 19 Series | 15 Series models in SiUS041501E; 19 Series models in SiUS041501E | coil-temperature-protection | Daikin A5 error code: freeze-up or peak-cut | On Daikin 15 and 19 Series equipment, A5 represents freeze-up protection in cooling or heating peak-cut control when the indoor heat-exchanger temperature crosses the documented limits. | The two meanings described here come from the Daikin service manual covering the 15 and 19 Series. Which protection you are looking at depends on the mode the system was running, and other Daikin ranges assign A5 within their own code structure, so start from the manual that matches your model plate. | Turn the unit off and inspect the user-removable filter for loading; clean it exactly as the model manual directs. | Confirm furniture, curtains, or closed louvers are not blocking the indoor intake or outlet. | Persistent icing, thermistor testing, coil cleaning beyond routine maintenance, and PCB diagnosis need qualified service. | Do not chip ice from a coil or use heat sources to force thawing. | Let visible ice thaw with the system off; if A5 returns after airflow is restored, stop cycling the unit and arrange diagnosis. | oem-service-manual | Daikin Comfort Technologies | 2026-09-02 | https://hvac-bench.com/brands/daikin/a5-error-code/ |
brands/daikin/a6-indoor-fan-motor | Daikin | daikin | A6 | ductless-mini-split | Daikin indoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV indoor equipment | FTXS series wall units; FXFQ series cassettes; FXMQ series ducted; FTXM series wall units | not-turning-on | Daikin A6: indoor fan motor locked, overloaded, or badly connected | Daikin lists A6 in the indoor unit division as a fan motor malfunction, described as the motor being locked, overloaded, or suffering from a faulty connection. All three are ways of saying the board commanded a fan speed and did not get the feedback it expected, so the code is about the command-and-feedback loop rather... | The definition here comes from the Daikin malfunction code chart, which is organised by division and detail code rather than by model. Indoor fan arrangements differ sharply between a wall unit, a cassette, and a ducted unit, so the mechanical cause behind the same code is model-specific and is read from that unit's se... | Switch the affected indoor unit off and leave it off, since running the outdoor unit against a stalled indoor coil is what the protection prevents. | Confirm the filters, front panel, and any decoration panel are correctly seated and latched after recent cleaning. | Write down any noise heard before the fault, the fan ... | Reaching into the fan housing, freeing a wheel, and testing motor feedback or winding condition require the indoor casing to be opened by a qualified technician. | Do not attempt to turn the fan wheel by hand through a grille or outlet. The blade edges and the drive arrangement are not designed for that access. | The code clears from the display on a power interruption, but the board re-tests the fan on the next start, so a fault that returns within seconds is reporting an unchanged mechanical or electrical condition. | mixed-primary-sources | Daikin Industries; Daikin Comfort Technologies | 2026-09-15 | https://hvac-bench.com/brands/daikin/a6-indoor-fan-motor/ |
brands/daikin/c9-suction-air-thermistor | Daikin | daikin | C9 | ductless-mini-split | Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems | FTXS series; FTXM series; FXFQ series; FXMQ series | temperature-sensor-fault | Daikin C9: the suction air thermistor the room setting depends on | Daikin places C9 in the sensor division against the suction air thermistor, and describes the fault as an abnormal resistance, which covers a disconnection and a short circuit. That sensor reads the air entering the indoor unit, so it is the value the system treats as room temperature and the basis of every capacity de... | The C division on the Daikin chart groups sensor systems, and the detail code selects which sensor. Where a sensor sits inside a particular indoor unit, and what resistance curve it follows, comes from the service manual for that model. A code alone does not tell a technician which physical part to reach for. | Note the unit number shown beside C9 and which room it serves before any power is interrupted. | Compare the temperature the controller displays, if it is still visible, against a separate thermometer near the intake. | Confirm filters and panels are correctly seated, and note whether the fault followed any recent clea... | Measuring thermistor resistance against the published curve and inspecting the indoor board connectors require the casing to be opened by a qualified technician. | A code accompanied by a burning smell, discoloration, or a protective device operating is a stop condition rather than a sensor question. | The resistance is measured again on the next start, so clearing the display does not change the outcome. A code returning immediately confirms the reading is still outside the accepted band. | oem-service-manual | Daikin Industries | 2026-09-15 | https://hvac-bench.com/brands/daikin/c9-suction-air-thermistor/ |
brands/daikin/e7-outdoor-fan-motor | Daikin | daikin | E7 | heat-pump | Daikin outdoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV outdoor equipment | RXS series; RXM series; RZQ series; RZR series | outdoor-unit-not-running | Daikin E7: the outdoor fan motor system stopped reporting what it should | Daikin places E7 in the outdoor unit division as a malfunction of the outdoor fan motor system. The word system is doing real work in that phrase: the entry covers the motor, the drive circuit that powers it, and the feedback path that confirms it turned. Seeing the fan stationary confirms the symptom but not the cause... | This meaning is taken from the Daikin malfunction code chart, which assigns codes by division rather than by model. Outdoor fan arrangements differ between a single-fan room air unit and a twin-fan SkyAir or VRV frame, and the checks for each come from the service manual covering that outdoor model. | Stop the system from the controller so it is not making repeated start attempts against a fan that is not turning. | Look at the outdoor unit from a safe distance and note whether the blade is completely static, turning slowly, or turning normally. | Isolate the outdoor unit at its dedicated switch before removing leav... | Testing the fan drive output, measuring motor windings, and inspecting feedback wiring inside an outdoor enclosure are energised tasks for a qualified technician. | Never reach through or remove the fan guard. A variable-speed outdoor fan can start without notice, including while the system appears to be idle. | A restart re-tests the fan within seconds, so the code returning quickly means the condition has not changed. Repeated attempts run the compressor briefly with no heat rejection, which is worth avoiding. | oem-service-manual | Daikin Industries; Daikin Comfort Technologies | 2026-09-15 | https://hvac-bench.com/brands/daikin/e7-outdoor-fan-motor/ |
brands/daikin/f3-discharge-pipe-temperature | Daikin | daikin | F3 | heat-pump | Daikin outdoor equipment covered by the SM-TS3 malfunction chart, spanning room air, SkyAir, and VRV outdoor units | RXS series; RXM series; RZQ series; RXYQ series | protection-shutdown | Daikin F3: discharge pipe temperature outside what the circuit allows | Daikin's malfunction chart lists F3 against discharge pipe temperature. The thermistor on the compressor discharge line has reported a temperature the control will not run at, and because refrigerant flow is what keeps that line cool, the reading is a statement about the circuit rather than about the pipe. | Taken from the Daikin After Sales Service malfunction chart, where the F division belongs to the outdoor unit and the detail code selects the subsystem. Sensor positions and the thresholds behind them come from the service manual for the specific outdoor model, so a code alone does not give you a temperature to compare... | Stop calling for heating or cooling and leave the system off, since each further cycle runs the compressor toward the same limit. | Walk the visible line set and outdoor unit looking for oil film or localised frost, and photograph anything unusual without touching it. | Record how long the outdoor unit runs before it s... | Charge measurement, leak detection, recovery, and discharge thermistor testing are certified refrigerant activities under EPA Section 608 and under F-Gas rules in the United Kingdom and European Union. | Adding refrigerant without finding the loss, or restarting to see whether the code stays away, both put the compress... | Power cycling clears the stored code and the protection re-evaluates on the next run. Because the measured temperature is a live condition, a code that returns quickly means nothing has changed in the circuit. | oem-service-manual | Daikin Industries; Daikin Comfort Technologies | 2026-09-15 | https://hvac-bench.com/brands/daikin/f3-discharge-pipe-temperature/ |
brands/daikin/u0-refrigerant-shortage | Daikin | daikin | U0 | ductless-mini-split | Daikin room air conditioner splits and multi-split systems that publish U0 in the malfunction code table | FTXS / RXS single-zone splits; FTXM series; MXS / MXL multi-zone outdoor units | low-refrigerant | Daikin U0 error code: refrigerant shortage on a mini-split | Daikin assigns U0 to a refrigerant shortage. The control has seen the circuit behaving as though there is too little refrigerant, from readings such as a low suction temperature or an abnormal discharge condition. A closed service valve, an undercharge left after install, or a leak all present as U0. | This meaning follows the Daikin malfunction code table for room air conditioner and multi-split systems that list U0. SkyAir, VRV, and Altherma ranges use their own code sets, so confirm the indoor and outdoor model numbers before applying this page. | Note whether the system is newly installed or has a long service history, and whether output faded gradually or stopped suddenly before U0. | Check from the ground for oily residue at pipe joints or unusual frosting on the outdoor unit, without touching the pipework or valves. | Refrigerant-circuit diagnosis and charging require a qualified technician with the applicable refrigerant handling credential. | Clearing U0 with a power cycle does not add refrigerant. If the code returns, the circuit is still short and the diagnosis needs gauges rather than another reset. | mixed-primary-sources | Daikin Comfort Technologies; Daikin Industries | 2026-09-09 | https://hvac-bench.com/brands/daikin/u0-refrigerant-shortage/ |
brands/daikin/u2-power-supply-fault | Daikin | daikin | U2 | heat-pump | Daikin equipment covered by the SM-TS3 malfunction chart, where the U division reports system-level conditions across room air, SkyAir, and VRV | RXS series; RZQ series; RXYQ series; FTXS series | voltage-protection | Daikin U2: power supply malfunction or an instantaneous power failure | In the Daikin malfunction chart, U2 belongs to the system division and reads as a malfunction of the power supply or an instantaneous power failure. That covers both a supply that briefly disappeared and a supply that is present but outside what the drive will work with, which is why one U2 after a storm and a U2 that ... | The reading is taken from the Daikin After Sales Service chart, where the U division covers system conditions rather than one unit. Some Daikin equipment, including the room air lines, presents a related shortage entry as U0, so confirm which digit is displayed before treating the fault as electrical. | Check whether a power cut, a storm, or electrical work coincided with the code, and write down what you find. | Confirm that the dedicated isolator and any protective device serving the equipment are in their normal operating position. | Read the supply voltage and frequency printed on the outdoor unit data plate so th... | Measuring supply voltage under load, inspecting isolator and terminal connections, and testing the drive input are qualified electrical tasks. | A protective device that operates repeatedly, a burning smell, or heat at an isolator is a stop condition. Leave the supply off and arrange an electrical inspection. | One restart is the accepted test for this entry because the chart includes an instantaneous power failure. If the code returns after that single attempt, leave the system off and treat the supply as the subject of the investigation. | oem-service-manual | Daikin Industries | 2026-09-15 | https://hvac-bench.com/brands/daikin/u2-power-supply-fault/ |
brands/daikin/u4-error-code | Daikin | daikin | U4 | light-commercial | SkyAir RZR-P and RZQ-P(9) | RZR-P series; RZQ-P(9) series; Compatible indoor units listed in SiUS281117 | communication-fault | Daikin U4 error code: indoor-outdoor transmission error | For the documented Daikin SkyAir RZR-P and RZQ-P(9) systems, U4 is a transmission error between indoor and outdoor units after normal communication is absent for the specified interval. | This definition is taken from the SkyAir service manual covering RZR-P and RZQ-P(9) equipment and the indoor units listed with it. Daikin uses structured code letters across product lines that share little else, so a U4 on VRV, Altherma, or a residential split needs the manual for that line rather than this page. | Write down the full controller code and every connected indoor and outdoor model number. | Check only normal user-accessible power controls and note whether other units on the same system operate. | Transmission wiring, fuses, fan motors, and PCBs require qualified electrical diagnosis. | Multi-unit SkyAir systems should be diagnosed as a network rather than by replacing the first board named. | A power cycle may be used only as the operating manual permits; a returning U4 indicates an unresolved transmission fault. | oem-service-manual | Daikin Comfort Technologies | 2026-09-02 | https://hvac-bench.com/brands/daikin/u4-error-code/ |
brands/daikin/ua-combination-fault | Daikin | daikin | UA | ductless-mini-split | Daikin split and multi-split systems that publish UA for an indoor and outdoor combination fault | FTXS / RXS splits; MXS / MXL multi-zone outdoor units; matched FTXM indoor units | combination-mismatch | Daikin UA error code: indoor and outdoor unit combination fault | Daikin assigns UA to an improper combination of indoor and outdoor units. The paired models are not compatible, the number of connected indoor units is outside the outdoor unit's limit, the refrigerant types do not match, or a replacement control board was fitted without its combination setting being made. | This meaning follows the Daikin malfunction code table for split and multi-split systems that list UA. SkyAir and VRV ranges assign UA-adjacent codes differently, so confirm the outdoor model and every connected indoor model before acting. | Note whether UA appeared at first commissioning, after equipment was combined from different kits, or right after a control board was replaced. | Write down the outdoor model and every indoor model with the room it serves, so the installer can check the combination against Daikin's data. | Changing paired equipment, removing indoor units from a multi-split, and making a replacement board's combination setting are all installer or technician tasks. | A power cycle does not change the equipment combination or a missing board setting, so UA returns until the underlying mismatch is corrected. Resetting is not a fix for this code. | mixed-primary-sources | Daikin Comfort Technologies; Daikin Industries | 2026-09-09 | https://hvac-bench.com/brands/daikin/ua-combination-fault/ |
brands/daikin/uf-piping-wiring-mismatch | Daikin | daikin | UF | ductless-mini-split | Daikin multi-split systems and splits that publish UF for a wiring and piping combination fault | MXS / MXL multi-zone outdoor units; 2MXS / 3MXS / 4MXS / 5MXS; matched FTXS and FTXM indoor units | wiring-piping-mismatch | Daikin UF error code: piping and wiring do not match | Daikin assigns UF to a mismatch between the control wiring and the refrigerant piping. On a multi-split the cable from an indoor head lands on one outdoor port while its pipes connect to a different port, so the system cannot pair a head with its circuit. It also covers wrong field wiring and a shortage detected during... | This meaning follows Daikin literature for multi-split and split systems that list UF as a field wiring and piping combination fault. Other Daikin ranges use different U-series codes, so confirm the outdoor unit and every connected indoor model before acting. | Note whether UF appeared at first commissioning or right after an indoor head was added, moved, or rewired, and which zones do not respond. | Keep a list of which room each indoor unit serves so the installer can match heads to outdoor ports quickly. | Tracing cables and pipes to outdoor ports and correcting the connections means opening the outdoor electrical cover and working at the terminals, which is installer work. | A power cycle does not change how the cables and pipes are connected, so UF returns until the port assignments are corrected. Resetting is not a fix for this code. | oem-service-manual | Daikin Comfort Technologies; Daikin Industries | 2026-09-09 | https://hvac-bench.com/brands/daikin/uf-piping-wiring-mismatch/ |
brands/daikin-altherma/7h-water-flow-subcodes | Daikin Altherma | daikin-altherma | 7H | heat-pump | Altherma 3 R MT with ELBH-E or ELBX-E and ERRA08-12 | ELBH-E(6V/9W); ELBX-E(6V/9W); ERRA08-12EV3; ERRA08-12EW1 | water-flow-fault | Daikin Altherma 7H subcodes: identify the failed flow check | On the documented Daikin Altherma 3 R MT, 7H is incomplete without its suffix. 7H-01 is a general water-flow problem; 7H-04 relates to domestic hot water, 7H-05 to heating or sampling, 7H-06 to cooling or defrost, 7H-07 to pump deblocking, and 7H-08 to pump feedback. | These subcodes belong to the ELBH-E and ELBX-E indoor units paired with ERRA08-12 equipment in the cited European installer reference. Other Altherma generations and monoblocs use different tables. | Capture the complete 7H suffix, both model labels, active mode, visible pressure, outdoor weather, pump sound, open zones, and recent hydraulic work. | Flow measurement, valves, filters, pumps, feedback, sensing, venting, configuration, electrical, and refrigerant work require an Altherma-qualified installer. | Do not clear the suffix before recording it or force pump functions; a returning 7H needs its exact hydraulic context diagnosed. | mixed-primary-sources | Daikin Europe; Daikin UK | 2026-09-03 | https://hvac-bench.com/brands/daikin-altherma/7h-water-flow-subcodes/ |
brands/daikin-altherma/hot-water-duty-faults | Daikin Altherma | daikin-altherma | Hot water duty conditions | heat-pump | Daikin Altherma air-to-water heat pump systems serving space heating and a domestic hot water cylinder | Altherma 3 H HT; Altherma 3 R; Altherma 3 M; Altherma integrated cylinder units | no-heating | Daikin Altherma hot water faults: two duties competing for one machine | An Altherma serves space heating and the hot water cylinder from one heat pump, and it cannot do both at once. Priority settings decide which duty wins, so heating that pauses during a cylinder reheat, or hot water that takes longer than a boiler did, is the system working as designed rather than reporting a fault. | Altherma covers split, monobloc, and integrated cylinder configurations across several generations, with different controllers and different parameter names. The installation and operation manual for your configuration governs, and hot water behaviour in particular depends on commissioning choices as much as on the har... | Note whether space heating pauses coincide with hot water production, which distinguishes priority switching from a fault. | Time a full cylinder reheat and record the cylinder temperature setting alongside it. | Check whether a disinfection cycle is scheduled and at what time, since that is when the element is expecte... | Cylinder temperature settings, priority parameters, and disinfection schedules affect both safety and running cost, and the installer who commissioned the system should change them. | Anything on the sealed refrigerant side of an Altherma needs a certified handler, regardless of whether the symptom appears on the hot w... | Priority switching and disinfection cycles are scheduled behaviour with nothing to reset. Confirm that a genuine fault code is displayed before treating the pattern as a failure. | mixed-primary-sources | Daikin UK; Daikin | 2026-09-15 | https://hvac-bench.com/brands/daikin-altherma/hot-water-duty-faults/ |
brands/della/outdoor-sensor-error-codes | Della | della | E3 / E7 / E8 / EH / Ej / En / Ey | ductless-mini-split | Econo IF, Vario TL, and Optima TP single zone, and the multi-zone systems sharing the table | Econo IF Series; Vario TL Series; Optima TP Series; Della multi-zone systems using the same table | outdoor-sensor-fault | Della outdoor sensor codes: the letter after E names the sensor | All seven codes report a failed outdoor temperature sensor, and the character after the E identifies which one. None of them is a compressor fault, a refrigerant fault, or an indoor fault. | This table is published for the Della Econo IF, Vario TL, and Optima TP single zone series, and the multi-zone systems that share it. The Motto JA and Umbra JPB series use a different set entirely, where outdoor sensor faults appear as F codes, so the series has to be established before any of this applies. | Photograph the display so the exact character after the E is preserved, since several of them are easy to misread. | Note whether the code is constant or intermittent, and what the weather was doing when it appeared. | Record any work carried out at the outdoor unit since the system last ran normally. | Sensor circuits, connectors, and their resistance measurements sit inside the outdoor electrical compartment and are technician work with the supply isolated. | Question any proposal to replace a compressor or a control board on the strength of a code from this sensor table. | One restart establishes whether the reading recovers. A code that returns immediately is reporting a circuit the control still cannot read, and further cycles remove the timing record rather than the fault. | oem-support | Della Home | 2026-09-03 | https://hvac-bench.com/brands/della/outdoor-sensor-error-codes/ |
brands/della/e5-error-code-by-series | Della | della | E5/5E | ductless-mini-split | Econo, Vario, Optima, Motto, and Umbra mini-splits | Econo IF Series; Vario TL Series; Optima TP Series; Motto JA Series; Umbra JPB Series | model-specific-code | Della E5 error code: the series changes the meaning | Della does not assign one universal meaning to E5. Its published table gives E5 as an indoor/outdoor mismatch on Econo, Vario, and Optima systems, but E5 or 5E as indoor/outdoor communication failure on Motto and Umbra systems. Read the model family before the code. | The distinctions here follow Della's own series table. They do not cover every Della generation, and a retail listing name is not a substitute for the model label when choosing the correct manual. | Photograph both model labels and the exact E5 or 5E orientation, then record whether the fault existed from initial commissioning. | Equipment matching, configuration, field wiring, voltage, communication, and board diagnosis belong to the installer or Della-authorised service. | Do not loop power; a returning E5 needs the series-specific mismatch or communication path, not another generic reset. | oem-support | Della Home | 2026-09-03 | https://hvac-bench.com/brands/della/e5-error-code-by-series/ |
brands/della/error-codes-by-series | Della | della | Series-dependent codes | ductless-mini-split | Della ductless mini-split systems documented in the Della manual and support library | Della single-zone wall units; Della multi-zone indoor units; Della outdoor condensing units | communication-fault | Della codes: a value brand still needs the right document | Della supports its equipment through documentation tied to each product line rather than through a single brand-wide code list. An owner therefore needs the model number before the code means anything, and that is the step most likely to be skipped on lower-cost equipment where the manual has been discarded. | Della equipment is manufactured to order and its documentation is organised per model. A code list found under the brand name alone may describe a different product line, and the manual or support document that matches the model number on the data plate is the only reliable mapping. | Photograph both data plates and record the complete model numbers before contacting anybody. | Photograph the displayed code before power is interrupted for any reason. | Note whether the system fails at startup or after a period of operation, and how long it ran. | The conductors linking the wall unit to the condenser sit at mains potential, which puts any probing, stripping, or reterminating of them outside owner work. | Conditions reached after a period of operation involve the sealed refrigerant circuit, which requires certification to open regardless of what the equipment cos... | One power interruption distinguishes a latched report from a live condition on this equipment as on any other. Photograph the code first, because on a system with no accessible chart the display is the only record you have. | oem-support | Della Home | 2026-09-15 | https://hvac-bench.com/brands/della/error-codes-by-series/ |
brands/drayton/one-room-not-heating | Drayton | drayton | Room demand not met | controls-thermostats | Drayton Wiser multi-zone heating systems using a heat hub with room thermostats and smart radiator thermostats | Wiser Heat Hub; Wiser Room Thermostat; Wiser Smart Radiator Thermostat | communication-fault | Drayton Wiser: one cold room when the rest of the house is warm | A Wiser system asks the boiler for heat only when at least one room wants it, and then opens that room's radiator valves. A single cold room therefore means either that room is not asking, or it is asking and its valve is not opening, and those are separate faults with separate fixes. | Wiser covers single-zone and multi-zone arrangements with different combinations of hub, room thermostats, and radiator thermostats, and behaviour depends on how the system was configured rather than only on what is installed. The Drayton Wiser documentation for your arrangement is the reference. | Confirm whether the rest of the house heats normally during the same period, which separates a room fault from a system fault. | Check and replace the batteries in the affected radiator thermostat, since a device without power cannot move a valve. | Listen at the radiator when a demand is set, since a valve that is bei... | A radiator that stays cold with its valve confirmed open, or that is cold at the bottom while hot at the top, is a hydraulic matter for a heating engineer. | Removing a radiator thermostat from a valve body, or changing a valve, risks releasing water from a sealed system and sits outside owner maintenance. | Removing and refitting batteries reconnects a device that has lost its link and does nothing for a valve that cannot move. Establish whether the valve is being driven before pairing anything again. | mixed-primary-sources | Drayton Controls; Schneider Electric | 2026-09-15 | https://hvac-bench.com/brands/drayton/one-room-not-heating/ |
brands/ecobee/threshold-and-staging-alerts | ecobee | ecobee | Alerts and reminders | controls-thermostats | ecobee smart thermostats with installer settings governing staging, thresholds, and equipment lockouts | ecobee Smart Thermostat Premium; ecobee Smart Thermostat Enhanced; ecobee3 lite | remote-not-working | ecobee alerts: settings the installer chose, reported back as problems | A large share of ecobee alerts report that a configured threshold was reached, not that equipment failed. Compressor lockout temperatures, staging differentials, and reminder intervals are all settings somebody chose during installation, and a thermostat behaving strictly according to them can look like a fault to whoe... | ecobee models differ in which settings they expose and under what names, and some are reachable only through installer settings rather than the everyday menus. The ecobee support material for your model is the reference for which threshold a given alert belongs to and where it is changed. | Read the full alert text rather than acting on its presence, since threshold and reminder alerts state what they are. | Record the outdoor temperature whenever auxiliary or emergency heat engages, so it can be compared against the configured lockout. | Note whether the alert began after a thermostat installation, an eq... | Installer settings govern how equipment stages and when it is locked out, and changing them without knowing the equipment can leave a heat pump running outside its intended envelope. | Alerts describing a sensor, a remote sensor link, or equipment that did not respond are measured conditions and need a technician rathe... | Dismissing an alert removes the message and leaves the setting that produced it in place. Where the alert describes a threshold, the fix is a configuration change rather than a reset. | oem-operation-manual | ecobee | 2026-09-15 | https://hvac-bench.com/brands/ecobee/threshold-and-staging-alerts/ |
brands/friedrich/floating-air-fault-indications | Friedrich | friedrich | Display indications | ductless-mini-split | Friedrich Floating Air ductless indoor units documented in the Friedrich product resource library | Floating Air Premier; Floating Air Pro; Floating Air Select | remote-not-working | Friedrich Floating Air: reading the display before reaching for a chart | A Friedrich Floating Air indoor unit uses one small display for three different jobs: reporting status, echoing a setting you have just changed, and reporting a fault. Characters that look alarming are frequently a mode indication or a confirmation, and separating the three is the first step rather than an afterthought... | The Floating Air range spans several generations with different displays and different capabilities, including models with and without built-in wireless control. The operation manual issued with your indoor unit is what maps a character to a meaning, and a chart written for another generation can be wrong. | Establish whether the unit still cools or heats when asked, since that alone separates most indications from genuine faults. | Press a remote button and watch whether the display changes and then reverts, which identifies a settings echo. | Photograph any persistent indication before interrupting power, and copy both m... | A persistent indication with operation stopped needs the indoor casing opened for testing, which is qualified work on this equipment. | Do not remove the front panel beyond the filter access the manual describes, since the same enclosure carries the supply to the board and the fan. | A power interruption clears mode and echo indications immediately and leaves a genuine fault report in place, which makes it a useful test as well as a reset. Photograph the display first. | mixed-primary-sources | Friedrich | 2026-09-15 | https://hvac-bench.com/brands/friedrich/floating-air-fault-indications/ |
brands/fujitsu/operation-and-timer-lamp-blink-codes | Fujitsu General | fujitsu | Lamp blink pattern | ductless-mini-split | Fujitsu General residential indoor units that report faults through operation and timer indicator lamps | Fujitsu RLS3 wall units; Fujitsu LZAS wall units; Fujitsu ARU ducted indoor units | communication-fault | Fujitsu blink codes: counting two lamps instead of one | Fujitsu indoor units without a character display report faults by blinking two indicator lamps in a coordinated pattern. The operation lamp and the timer lamp each carry a count, and the fault is identified by the pair rather than by either one, which is why counting only the light that first catches your eye produces ... | This convention belongs to Fujitsu General residential indoor units that use indicator lamps rather than a numeric display. Fujitsu equipment with a wired controller shows codes directly, and the lamp tables differ between indoor generations, so the operation manual for your own model is the reference. | Film the lamp pattern on a phone through at least three full repetitions before interrupting power for any reason. | Count each lamp separately from the recording and write both numbers down with the date. | Confirm whether the unit still acknowledges commands from the remote control. | Interpreting the pair against the service tables, testing sensing elements, and checking the interconnecting cable require the casing to be opened by a qualified technician. | An outdoor protection reported through the indoor lamps involves the refrigerant circuit, which is certified work rather than an owner check. | Interrupting power stops the pattern and can clear what the unit was reporting, so capture the recording first. One restart afterwards shows whether the same pattern returns. | mixed-primary-sources | Fujitsu General | 2026-09-15 | https://hvac-bench.com/brands/fujitsu/operation-and-timer-lamp-blink-codes/ |
brands/ge-appliances/zoneline-ptac-fault-indications | GE Appliances | ge-appliances | Zoneline fault indications | ductless-mini-split | GE Zoneline packaged terminal air conditioners and heat pumps documented in GE Appliances owner and support material | Zoneline AZ45; Zoneline AZ65; Zoneline AZHS heat pump models | not-turning-on | GE Zoneline faults: a PTAC is one box with everything in it | A GE Zoneline is a packaged terminal unit, meaning the compressor, both coils, the fans, and the controls all sit in one chassis through the wall. That changes how a fault reads: there is no interconnecting cable to suspect, no separate outdoor unit to check, and every component behind a code is inside one sleeve. | Zoneline covers cooling-only and heat pump models across several generations, with different control boards and different indications. GE Appliances publishes owner and support material per model, and the code or indication on your unit is read against that rather than against a general PTAC chart. | Remove, clean, and refit the filter according to the owner manual, letting it dry fully before it goes back. | Look at the exterior grille and clear obstructions that can be reached without removing it. | Note whether other units in the same building are behaving the same way, and how many. | Withdrawing a chassis from its wall sleeve, testing the control board, and any refrigerant work are service tasks on this equipment. | A packaged unit carries mains supply and a sealed refrigerant circuit inside the same chassis as the filter access, so the boundary for owner work is the filter and the front panel. | Power interruption clears an indication and the unit re-tests its conditions on restart. Where airflow or charge is behind the fault, the indication returns as soon as the unit works hard enough to meet the same limit. | mixed-primary-sources | GE Appliances | 2026-09-15 | https://hvac-bench.com/brands/ge-appliances/zoneline-ptac-fault-indications/ |
brands/goodman/gmvc-one-flash-lockout | Goodman | goodman | 1 flash | furnace | GMVC80 condensing gas furnaces | GMVC801005CN; GMVC80 family covered by the cited installation instructions | ignition-lockout | Goodman GMVC one flash: external ignition lockout | On the documented Goodman GMVC80 control, one flash indicates external lockout after the furnace exceeds its ignition attempts. The control can automatically reset after one hour, while a thermostat or power interruption longer than five seconds can also reset it; none of those actions diagnoses why flame was not prove... | This one-flash definition applies to the GMVC80 family in the cited Goodman installation instructions. Other Goodman boards use different LEDs and decimal codes, so identify the furnace and control before counting. | Keep furnace panels installed, record one full startup sequence and the repeating flash, and stop without creating additional ignition attempts. | Draft, vent, condensate, igniter, gas, burner, flame-current, grounding, safety, and control tests require licensed gas-furnace service. | Do not use the published reset paths to keep forcing ignition; a returning one-flash lockout needs its failed sequence stage diagnosed. | mixed-primary-sources | Goodman | 2026-09-03 | https://hvac-bench.com/brands/goodman/gmvc-one-flash-lockout/ |
brands/goodman/furnace-two-flashes-pressure-switch-closed | Goodman | goodman | 2 flashes | furnace | Goodman GMVC-series two-stage variable-speed gas furnaces documented in the installation and operating instructions | GMVC80; GMVC95; GMVC96 | pressure-switch-fault | Goodman two flashes: the pressure switch is closed when it should be open | Two flashes on a Goodman integrated control reports the pressure switch circuit closed at a point in the sequence where the control expects it open. The control checks the switch before the inducer runs, and a circuit already made at that moment means the switch cannot prove anything about draft once the inducer starts... | Take this from the diagnostic table printed in the Goodman GMVC-series installation and operating instructions. Goodman has used other flash counts on earlier and later control platforms, and Amana equipment built on related controls publishes its own table. Take the count from the label inside your own furnace door. | Read the flash count through the door sight glass rather than removing the blower door, since opening it can cut control power and clear the code. | Confirm the thermostat is set to heat, is calling, and has good batteries if it uses them. | Look for standing water or staining around the base of the furnace and note an... | Testing a pressure switch, clearing condensate tubing, and inspecting the inducer and vent path are licensed gas-furnace tasks. | Never bridge, jumper, or bypass a pressure switch to make a furnace run. The switch is the only thing confirming that combustion products are leaving the building. | Cutting power clears the stored code, and the control repeats the same pre-start check on the next call for heat. A code that returns immediately is reporting a switch state that has not changed. | mixed-primary-sources | Goodman | 2026-09-15 | https://hvac-bench.com/brands/goodman/furnace-two-flashes-pressure-switch-closed/ |
brands/goodman/gmvc80-three-flashes-pressure-switch-open | Goodman | goodman | 3 flashes | furnace | Goodman GMVC80 condensing gas furnaces | GMVC80 family covered by the cited installation instructions | pressure-switch-open | Goodman GMVC80 three flashes: pressure switch open after the inducer starts | On the documented Goodman GMVC80 board, three flashes means the pressure-switch circuit is open when the control expects it closed. It does not prove the pressure switch is defective. The inducer, venting, condensate path, hose, wiring, and available draft all remain part of the diagnosis. | This three-flash definition belongs to the GMVC80 instructions cited here. Newer Goodman furnaces can use alphanumeric seven-segment codes instead of this LED pattern, so match the model and the legend on its door before applying the meaning. | Listen to one complete heat-call sequence with every furnace panel installed and record whether the inducer starts before the code. | Look at accessible outdoor intake and exhaust openings for visible snow, leaves, nests, or damage without inserting anything. | Photograph the flash pattern twice and capture the model n... | Pressure measurement, hose and condensate inspection, switch testing, vent assessment, and live electrical diagnosis require qualified gas-furnace service. | Never bypass a pressure switch or hold a panel interlock to force an ignition attempt. | Do not use repeated power cycles as a repair. A returning three-flash state means the furnace still lacks the pressure-switch proof required to ignite. | mixed-primary-sources | Goodman | 2026-09-09 | https://hvac-bench.com/brands/goodman/gmvc80-three-flashes-pressure-switch-open/ |
brands/goodman/furnace-four-flashes-open-limit | Goodman | goodman | 4 flashes | furnace | Goodman and Amana single-stage and two-stage gas furnaces with an integrated ignition control | GMVC80; GMEC96; GCVC96; GMES80 | limit-switch-fault | Goodman furnace 4 flashes: open high-limit circuit | Four flashes on a Goodman furnace control means the primary limit circuit is open. The limit is a temperature safety that trips when the air leaving the heat exchanger is too hot, so the fault points at restricted airflow or poor heat transfer rather than at a failed switch. | This meaning applies to Goodman and Amana gas furnaces whose control legend lists four flashes as an open limit or open high-limit circuit. Flash-code meanings differ between control boards, so read the label inside the furnace blower door for the exact model. | With the furnace off, replace a loaded filter with the correct clean size, arrow pointing toward the blower, and confirm supply and return grilles are open and unblocked. | Note whether the four-flash code clears with airflow restored and whether it returns on the first or second heating stage. | Measuring temperature rise and static pressure, inspecting the blower motor, capacitor and wheel, and testing or replacing the limit switch are technician tasks, and the limit must not be bypassed. | The furnace attempts to restart on its own once the limit cools and remakes. If four flashes returns after airflow is restored, leave it for service rather than forcing repeated cycles. | mixed-primary-sources | Goodman | 2026-09-09 | https://hvac-bench.com/brands/goodman/furnace-four-flashes-open-limit/ |
brands/goodman/furnace-five-flashes-flame-out-of-sequence | Goodman | goodman | 5 flashes | furnace | Goodman GMVC-series two-stage variable-speed gas furnaces documented in the installation and operating instructions | GMVC80; GMVC95; GMVC96 | flame-out-of-sequence | Goodman five flashes: flame sensed when no flame should exist | Five flashes on a Goodman integrated control reports flame sensed when there was no call for heat and the gas valve should have been closed. The control is describing gas burning outside the sequence it commanded, which is why the response is to shut down and involve a licensed engineer rather than to reset and observe... | What follows is scoped to GMVC-series equipment and the flash table Goodman prints for it. Other Goodman control generations, and related brands built on similar boards, assign this count differently, so the diagnostic label fixed inside your own furnace door is the authority rather than any chart found elsewhere. | Check for any smell of gas indoors, and if one is present leave the property and use the emergency number your gas supplier publishes before doing anything else. | Switch the furnace off at its dedicated service switch so the control stops attempting cycles. | Note whether you actually saw or heard burner activity, or ... | A gas valve that does not seat, a burner alight outside its commanded sequence, and flame sensing circuit faults are licensed gas engineering work without exception. | Do not operate, reset, or test the furnace to see whether the code returns. The condition being reported is combustion the control did not ask for. | null | oem-service-manual | Goodman | 2026-09-15 | https://hvac-bench.com/brands/goodman/furnace-five-flashes-flame-out-of-sequence/ |
brands/goodman/furnace-six-flashes-rollout-or-polarity | Goodman | goodman | 6 flashes | furnace | Goodman GMVC-series and related integrated furnace controls documented in the installation and operating instructions | GMVC80; GMVC95; GMVC96; AVPVC air handler controls | limit-circuit-lockout | Goodman six flashes: a rollout trip and a wiring fault on one count | Six flashes is a count that Goodman has assigned differently on different integrated controls, including a flame rollout trip on some and a line voltage polarity or grounding condition on others. Because those two readings have completely different risk levels, the diagnostic label inside your own furnace door decides ... | Goodman publishes the flash-count table on the wiring and diagnostic label of each furnace and in that model's installation and operating instructions. The count-to-meaning mapping is a property of the control platform, so a table from a different Goodman generation, or from Amana equipment on a related control, can be... | Read the diagnostic label inside the furnace door through the sight glass or during a permitted access, and record what six flashes is assigned to on that control. | Look and smell for soot, scorching, or combustion odours around the furnace without opening the burner compartment. | List any electrical work, supply cha... | A flame rollout trip requires combustion, heat exchanger, and venting assessment by a licensed gas engineer, and the reset button on a rollout device is not an owner control. | Correcting line voltage polarity or a grounding fault at the furnace supply is electrical work for a qualified person, not a matter of swapping... | Where the count corresponds to a rollout trip, there is no owner reset: the device exists to stay open until the cause is found. Where it corresponds to a polarity or grounding condition, nothing clears until the supply is corrected. | oem-service-manual | Goodman | 2026-09-15 | https://hvac-bench.com/brands/goodman/furnace-six-flashes-rollout-or-polarity/ |
brands/goodman/furnace-seven-flashes-low-flame-signal | Goodman | goodman | 7 flashes | furnace | Goodman and Amana gas furnaces with an integrated ignition control that flashes seven for low flame signal | GMEC96; GMVC96; GCES80; GMES96 | flame-sense-fault | Goodman furnace 7 flashes: weak flame sense signal | Seven flashes on a Goodman furnace control means the flame sense current has fallen below the level the board needs to confirm a flame. The burner lights, but the control does not read enough microamps of rectified current, so it closes the gas valve and retries, then locks out after a set number of trials. | This meaning applies to Goodman and Amana furnaces whose control legend lists seven flashes as a weak or low flame signal. Boards differ, so a furnace showing seven flashes for a different fault should be read against the label inside its blower door. | Watch a start-up cycle and note that the burner does light before it drops out, and count how many attempts happen before the lockout. | Confirm the furnace door is fully closed and the filter is clean, then leave the panel in place for a technician to open. | Cleaning or replacing the flame sense rod, checking the burner ground, measuring flame current, and adjusting gas pressure all require a qualified heating technician working inside the furnace. | The control retries on its own and then locks out. A single power cycle to clear the lockout is reasonable, but a return to seven flashes means the signal is still weak and the furnace needs service. | mixed-primary-sources | Goodman | 2026-09-09 | https://hvac-bench.com/brands/goodman/furnace-seven-flashes-low-flame-signal/ |
brands/goodman/comfortnet-eb0-eb1-eb3-in-cooling | Goodman | goodman | b0, b1, b3 | air-handler | Goodman and Amana variable-speed air handlers with an integrated control module reporting motor codes on a seven-segment display and through a ComfortNet thermostat | Goodman AVPVC series variable-speed air handlers; Goodman air handlers using the PCBJA integrated control module family; ComfortNet thermostats paired with those air handlers | blower-limiting-condition | Goodman ComfortNet Eb0, Eb1 and Eb3 in cooling: why an airflow code appears while heating still works | Read them apart. The b3 entry is the only airflow condition of the three. Goodman describes it as the circulator blower motor operating in a power, temperature or speed limiting condition, and lists blocked filters, restrictive ductwork, undersized ductwork and high ambient temperature as the causes. The b0 entry says ... | These codes belong to the air handler integrated control module, and the seven-segment display alternates characters, which is why written transcriptions vary between readers. Furnace and outdoor unit codes on the same ComfortNet system come from separate tables. | Check the filter and replace or clean it according to the equipment instructions, because blocked filters are on the published cause list. | Confirm that supply registers and return grilles are fully open and unobstructed. | Record whether the code appears in cooling, in heating, or in both, and whether the blower ran ... | Any work on motor power leads, motor control leads or the integrated control module is inside an energised cabinet and is service work. | Duct static pressure measurement and duct sizing assessment need instruments and belong to a technician. | Removing power clears the display and loses the order the codes appeared in. Photograph the seven-segment display through its full alternating sequence before interrupting anything. | oem-service-manual | Goodman | 2026-09-04 | https://hvac-bench.com/brands/goodman/comfortnet-eb0-eb1-eb3-in-cooling/ |
brands/nest/delayed-message-and-power | Google Nest | nest | Delayed | controls-thermostats | Google Nest learning and programmable thermostats that report power and delay conditions on screen | Nest Learning Thermostat; Nest Thermostat E; Nest Thermostat | communication-fault | Nest delayed messages: the thermostat is rationing its own battery | A Nest thermostat that says heating or cooling is delayed has detected that its internal battery is low and is postponing the call while it charges. Nothing needs to be wrong with the heating system at all. The thermostat is protecting its own ability to keep running, and the question worth asking is why it is not char... | This covers Google Nest thermostats that draw charge from the heating system wiring. Behaviour differs between Nest generations and between installations with and without a dedicated common conductor, so the Google support material for your specific model is the reference. | Note how often the delay message appears and whether it is worse in cold weather when the heating runs more. | Confirm that the heating itself works once the delay expires, which separates the control from the appliance. | Check whether a battery or power message has appeared alongside the delay at any point. | Running a new conductor to the thermostat position, or altering connections at a Heat Link or equipment terminal, is electrical work for a qualified person. | Do not add a conductor at the equipment end without knowing what it lands on. Heating control wiring carries mains voltage on many United Kingdom installations. | Restarting the thermostat clears the message and does nothing for the charge that produced it. Where the arrangement cannot keep up, the message returns as soon as the heating is used again. | oem-support | Google Nest | 2026-09-15 | https://hvac-bench.com/brands/nest/delayed-message-and-power/ |
brands/nest/e73-no-power-rc | Google Nest | nest | E73 | controls-thermostats | Google Nest Learning Thermostat and Nest Thermostat | Google Nest Learning Thermostat; Google Nest Thermostat; Google Nest Thermostat E | thermostat-power-loss | Nest E73: no power to the Rc wire, and the cooling side behind it | These codes report that the thermostat is no longer receiving 24 volt power on a named wire. Google groups E3, E23, and E73 as no power to the Rc wire, E4, E24, and E74 as no power to the Rh wire, and E195 as no power to the R wire, so the letter in the message identifies which transformer feed went quiet rather than w... | This page is written around the Rc group of Nest help codes. HVAC Bench covers the Rh group, headed by E74, on its own page, and the two should not be read across: on a two-transformer installation they point at different equipment in different parts of the building. Whether your system has separate Rc and Rh feeds at ... | Check the breakers for the heating and the cooling equipment and the service switch beside the furnace or air handler. | Replace the air filter if it is dirty, which Google includes in its own troubleshooting sequence. | Look for water in the drip pan or a blocked drain tube under the indoor unit. | Turn off power to b... | A blown or blackened system fuse, whose cause needs to be found before replacement. | A condensate blockage that needs the drain line cleared. | An absent 24 volt supply once breakers, switches, and wiring have been confirmed correct. | Any equipment panel that would need to be opened to reach a transformer or a safety... | There is no reset that clears these codes while the supply is missing. The message goes away when 24 volts returns to the named terminal, so restoring the breaker, the switch, or the drainage is the reset. If the internal battery has drained, allow charging time after power returns before judging whether the fault has ... | oem-support | Google Nest; Trane | 2026-09-08 | https://hvac-bench.com/brands/nest/e73-no-power-rc/ |
brands/nest/e74-no-power-rh | Google Nest | nest | E74 | controls-thermostats | Google Nest thermostats covered by the E-code power guide | Nest Learning Thermostat; Nest Thermostat E | thermostat-power-fault | Nest E74: no power detected on the Rh wire | Google Nest defines E74 as no power detected on the Rh wire. The thermostat is reporting the missing 24-volt heating-power input, not its cause. Furnace power, transformer and fuse, equipment safeties, condensate devices, Rh wiring and connection, and the thermostat input remain separate diagnostic points. | This E74 definition applies to Nest models covered by Google's wiring-error guide. The 2020 Nest Thermostat can present different messages, and Rc, C, and other E-codes identify different inputs. | Save the E74 and wiring screen, identify whether equipment also lost power, and switch HVAC power off before any manual-approved connector inspection. | Transformer, fuse, equipment safety, condensate control, concealed wiring, voltage measurement, and thermostat-input diagnosis require qualified HVAC service. | Do not reset-loop E74 or bypass a safety; restore only a known normal power switch and preserve a returning no-Rh condition for diagnosis. | mixed-primary-sources | Google Nest | 2026-09-03 | https://hvac-bench.com/brands/nest/e74-no-power-rh/ |
brands/grant/aerona-alarm-handling | Grant | grant | Aerona alarm codes | heat-pump | Grant Aerona air source heat pumps documented in the Grant fault and support material | Aerona3; Aerona 290; Aerona R32 range | protection-shutdown | Grant Aerona alarms: a heat pump in a house built for a boiler | Grant Aerona alarms divide between the sealed refrigerant side of the heat pump and the water circuit it serves, and the second group is where most retrofit installations end up. A heat pump moves far more water than the boiler it replaced, so a circuit that was adequate before can leave the appliance short of flow. | The Aerona name covers several generations with different refrigerants and different controllers, and the alarm set differs between them. Take the model and serial number from the outdoor unit and read the alarm against Grant documentation for that unit rather than a general heat pump list. | Photograph the controller showing the alarm before anybody clears it, together with any text alongside the number. | Write down how cold it was outdoors and what flow temperature the controller had been calling for when the alarm arrived. | Feel every radiator and underfloor manifold during a heating period and map whi... | Where an alarm sits on the sealed side of the machine, only a certified person may open it: the F-Gas framework governs that in Britain and the European Union, and Section 608 does the equivalent job in the United States. | Adjusting pump settings, balancing a circuit, or altering emitters on a heat pump installation s... | Expect the system to run again once an alarm is cleared, and to keep running until the weather asks for the same output. What identifies a marginal circuit is the shape of a whole winter, so keep a note of every occurrence rather than the most recent one. | oem-support | Grant UK | 2026-09-15 | https://hvac-bench.com/brands/grant/aerona-alarm-handling/ |
brands/gree/e5-overcurrent-low-voltage | Gree | gree | E5 | ductless-mini-split | Gree residential mini-splits that publish E5 in the protection code family | Sapphire; Livo; Vireo; Multi21+ indoor heads | voltage-protection | Gree E5 error code: overcurrent and supply voltage protection | Gree assigns E5 to an overcurrent protection trip. The control has seen the compressor circuit draw more current than its limit, and Gree links this to a supply voltage that is too high or that sags and swings under load. It points at the electrical supply, the connections, or the compressor and its drive rather than o... | This reading follows the Gree code overview and service literature for the residential mini-split families that publish E5 as a protection code. Other Gree ranges and other brands can map these characters differently, so match the indoor and outdoor model plates first. | Note whether E5 trips coincide with other large appliances running and whether the lights dim when the outdoor unit starts. | Check that the isolator switch by the outdoor unit is fully on and shows no scorching or a burnt smell, without opening it. | Measuring supply voltage under load, checking the feed size, inspecting energised connections, and testing the capacitor, contactor, and compressor current require a qualified technician or electrician. | One restart shows whether E5 was a single event. If it returns, especially under load, leave the system off, because repeated overcurrent trips stress the compressor and drive. | mixed-primary-sources | Gree Comfort | 2026-09-09 | https://hvac-bench.com/brands/gree/e5-overcurrent-low-voltage/ |
brands/gree/e6-error-code | Gree | gree | E6 | ductless-mini-split | Multi21+ and documented residential mini-splits | Multi21+ 30K; Multi21+ 36K; Multi21+ 42K | communication-fault | Gree E6 error code: indoor-outdoor communication fault | On the documented Gree systems, E6 means the indoor and outdoor equipment are not communicating normally; it identifies a communication path fault, not a single failed part. | This meaning follows Gree literature for the Multi21+ capacities and the residential systems named in the manufacturer support article. Other Gree ranges, and the same characters on another brand, can be assigned to a different fault, so match the model plate before you use this page. | Record the complete indoor and outdoor model numbers and photograph the E6 display. | With the system off, confirm no recent breaker trip, outage, or visible cable damage occurred. | A technician should isolate power before inspecting terminals, wiring continuity, accessories, or control boards. | Do not perform the manual's powered voltage tests unless you are qualified for live electrical diagnostics. | One power cycle may confirm whether the code was transient; repeated E6 requires diagnosis and should not be repeatedly reset. | mixed-primary-sources | Gree Comfort | 2026-09-02 | https://hvac-bench.com/brands/gree/e6-error-code/ |
brands/gree/e7-error-code | Gree | gree | E7 | multi-zone | Multi21+ and the residential ranges in the Gree code overview | MULTI30HP230V1BO; MULTI36HP230V1BO; MULTI42HP230V1BO | mode-conflict | Gree E7 error code: two indoor units asking for different modes | Gree assigns E7 to a mode conflict: two or more indoor units on the same outdoor unit have been set to modes the system cannot run at once. Nothing has failed, and setting the heads to one agreed mode clears it. | This meaning follows the Gree manufacturer code overview and the Multi21+ 30K, 36K, and 42K service manual. A single-zone Gree system has no second head to disagree with, and other manufacturers assign E7 to unrelated faults, so read the plate before applying anything here. | Read the mode symbol on every indoor unit in the property, including heads in rooms nobody is using. | Stop every head from its own handset, then start only the room you want, and note whether E7 returns. | Photograph both rating plates and the E7 display before contacting service, in case the code survives the checks ... | A conflict code that remains after every head has been set to one mode needs a technician with the wiring diagram for your capacity. | Do not remove indoor or outdoor electrical covers to look for a stuck mode signal; that work belongs behind an isolated supply. | Setting every indoor unit to one mode is the documented way to clear a mode conflict. Cutting the supply to force a restart does not resolve a disagreement the heads will have again the moment they are switched back on. | mixed-primary-sources | Gree Comfort | 2026-09-03 | https://hvac-bench.com/brands/gree/e7-error-code/ |
brands/gree/f1-indoor-ambient-sensor | Gree | gree | F1 | ductless-mini-split | Gree residential mini-split indoor units using the F-series sensing bulb codes described in Gree North America support | Gree Livo wall units; Gree Vireo wall units; Gree Sapphire wall units; Multi21 indoor units | temperature-sensor-fault | Gree F1: the indoor ambient sensing bulb is open or shorted | Gree assigns F1 to the indoor ambient temperature sensing bulb being open or short circuited. That bulb reads the air entering the indoor unit, which the system treats as the room temperature, so once the reading leaves its acceptable range the control has no reference against which to compare the set point. | Gree publishes the F-series sensing entries for its residential mini-split range. Gree also manufactures under other brand names, and a unit sold under a partner brand may present a different code set even where the hardware is related. Check the code against the manual supplied with your own indoor unit. | Read the two characters carefully and confirm it is F1 rather than F2 or another F-series entry, since the digit selects the sensor. | Compare the temperature the indoor unit reports with a thermometer placed near the intake, and record both. | Make sure nothing was left half-fitted after the last clean, particularly t... | Gree places sensing bulb faults among the categories requiring a licensed technician, and the components sit inside the indoor casing. | Do not open the indoor unit to inspect or reseat a sensor connector. The same enclosure carries the supply to the board and the fan motor. | Killing the supply blanks the display for a moment, then the board takes the same measurement again as soon as it wakes. An F1 that comes straight back is describing a resistance that never moved. | oem-support | Gree Comfort | 2026-09-15 | https://hvac-bench.com/brands/gree/f1-indoor-ambient-sensor/ |
brands/gree/f2-evaporator-sensing-bulb | Gree | gree | F2 | ductless-mini-split | Gree residential mini-split indoor units using the F-series sensing bulb codes described in Gree North America support | Gree Livo wall units; Gree Vireo wall units; Multi21 indoor units; Gree cassette indoor units | temperature-sensor-fault | Gree F2: losing the coil sensor removes the freeze protection | Gree assigns F2 to the indoor evaporator sensing bulb being open or short circuited. That bulb sits on the indoor coil rather than in the air stream, and its reading is what freeze protection and cold-draught prevention are built on, so the unit stops rather than run those functions without a value it can trust. | The F-series entries described here belong to Gree residential mini-split equipment. Equipment manufactured by Gree and sold under a partner brand can present its own code set and its own sensor arrangement, so match the code to the manual issued with your indoor unit rather than to the manufacturer behind it. | Select fan-only operation if ice is present and let the coil thaw without applying heat, water, or any tool to it. | Photograph any frost or ice before it melts, since the pattern of where it formed is useful to service. | Note whether heating had been slow to blow warm air in the weeks before the code appeared. | A bulb clamped to refrigerant tubing behind the front panel is not owner-accessible, and Gree assigns this class of fault to a licensed technician. | Repeated indoor coil icing needs airflow and refrigerant assessment, which is certified work rather than something to diagnose from the room. | Clearing the display does not change the resistance at the coil, and the board reads it again immediately. Treat a returning F2 as confirmation that the sensing path is still outside its band. | mixed-primary-sources | Gree Comfort | 2026-09-15 | https://hvac-bench.com/brands/gree/f2-evaporator-sensing-bulb/ |
brands/gree/h5-error-code | Gree | gree | H5 | heat-pump | Gree residential inverter systems covered by the OEM guide | Gree residential inverter systems; verify the model service manual | inverter-module-protection | Gree H5 error code: intelligent power module protection | Gree identifies H5 as intelligent power module protection caused by an IPM synchronization or overcurrent condition; the protection can have airflow, refrigerant, wiring, board, or compressor causes. | H5 as described here follows the Gree technical guide for residential inverter systems. Protection codes are tied to a specific drive design, so confirm the service manual for your model before treating this as the definition, and never assume a Gree code carries across to another manufacturer. | Turn the system off and look for a blocked return filter or obvious debris restricting the outdoor coil. | Record whether H5 appears immediately or only after the compressor begins operating. | Refrigerant pressure, compressor winding, DC bus, and live-voltage tests are technician work. | Do not replace a board or compressor until the root operating condition is confirmed. | A single restart can document recurrence, but repeated clearing does not correct an overcurrent or inverter protection condition. | oem-support | Gree Comfort | 2026-09-02 | https://hvac-bench.com/brands/gree/h5-error-code/ |
brands/haier/e5-overcurrent-protection | Haier | haier | E5 | ductless-mini-split | Haier residential split air conditioners documented in the Haier service and resource library | Haier Forward series; Haier Flexis series; Haier Pearl series | voltage-protection | Haier E5: overcurrent stops are as much about the supply as the unit | Haier uses E5 for an overcurrent condition, meaning the current drawn exceeded what the control permits. Current is a product of the work being demanded and the voltage available to do it, so a low or unstable supply produces the same code as a compressor that is hard to turn. | This applies to Haier residential split equipment documented in the Haier service library. Haier manufactures for several brand programmes, and units sold under other names may use a different code set even where hardware overlaps. Confirm against the manual issued with your own unit. | Make one start attempt and note how long the outdoor unit runs before the code returns. | Watch whether household lighting reacts at the moment of start, and note the time of day each occurrence happens. | Confirm no protective device in the consumer unit or panel has operated, and that the unit is on the supply arrang... | Measuring supply voltage under starting load, testing compressor windings, and assessing the drive are energised tasks for a qualified person. | A protective device that trips when the unit starts, a burning smell, or heat at an isolator means leaving the supply off and arranging an electrical inspection before anythin... | Allow yourself a single attempt and then stop. Everything after the first try simply re-runs the surge that tripped the protection, and none of those attempts tells you anything the first one did not. | mixed-primary-sources | Haier Appliances | 2026-09-15 | https://hvac-bench.com/brands/haier/e5-overcurrent-protection/ |
brands/haier/forward-series-e7-error | Haier | haier | E7 | ductless-mini-split | Forward Series | Haier Forward Series indoor and outdoor units | communication-fault | Haier Forward Series E7 communication fault | On Haier Forward Series systems, indoor code E7 identifies a communication failure between the indoor and outdoor units; the outdoor diagnostic can report the same condition with 15 flashes. Wiring, connections, supply, and either control end remain candidates until the communication path is tested. | This definition comes from Haier's North American Forward Series service manual. Other Haier families reuse E7 for different conditions, so the series and both model labels must match before this meaning is applied. | Save the indoor display, both rating plates, whether the system ever ran, and the timing of any outage, storm, installation, or repair. | Outdoor flash observation behind a cover, cable tests, terminal correction, voltage measurement, and board diagnosis belong to qualified service. | Perform no more than one model-permitted restart; a returning E7 should be diagnosed along the communication path. | mixed-primary-sources | Haier Appliances | 2026-09-03 | https://hvac-bench.com/brands/haier/forward-series-e7-error/ |
brands/haier/forward-series-f11-f28 | Haier | haier | F11 / F28 | ductless-mini-split | Forward Series systems in the manufacturer service manual | Haier Forward Series indoor and outdoor units covered by the cited service manual | compressor-drive-fault | Haier Forward F11 and F28: compressor position not detected | Both codes report that the position of the compressor rotor cannot be detected normally. The service manual gives the decision conditions as compressor wiring that is wrong or poorly connected, or a damaged compressor, so the code covers a wide range of repair. | This follows the Haier service manual for the Forward Series, where the codes appear as indoor display F11 and F28 alongside outdoor LED1 flash counts of 18 and 19. Haier assigns codes by product family, and the Forward Series is documented in its own literature, so confirm the range before applying these meanings. | Photograph the indoor display, or count two complete flash cycles at the outdoor board and write the number down. | Record whether any work has been done at the outdoor unit, and by whom, since the system last ran normally. | Note whether the outdoor fan turns at all when the system is asked to start, without opening a... | Compressor terminals, drive circuits, and winding measurements are technician work with the supply isolated and the capacitors discharged. | Ask for the compressor to be tested rather than inferred, because the manual lists wiring and a damaged compressor as alternatives under the same code. | One controlled restart tells you whether the code survives a power interruption. Repeating it asks a drive to keep starting a motor it cannot locate, so stop after the first attempt. | mixed-primary-sources | Haier Appliances | 2026-09-03 | https://hvac-bench.com/brands/haier/forward-series-f11-f28/ |
brands/hisense/hi-ultra-xtreme-code-16 | Hisense | hisense | 16 | ductless-mini-split | Hi-Ultra Xtreme R-454B | Hi-Ultra Xtreme 454B models covered by the sensor service manual | temperature-protection | Hisense Hi-Ultra Xtreme code 16 changes with operating mode | On the documented Hisense Hi-Ultra Xtreme 454B family, code 16 is mode-dependent: in cooling it reports indoor-coil antifreeze protection, while in heating it reports an overload protection condition. Record the active mode because the same number leads to a different diagnostic branch. | This dual meaning belongs to the Hi-Ultra Xtreme R-454B service literature cited here. It must not be applied to Hisense portable appliances, dehumidifiers, other refrigerants, or unrelated ductless series. | Preserve the active mode, photograph code 16, inspect only accessible filters and clearances, and let visible ice thaw without tools or added heat. | Sensor, fan, refrigerant, pressure, wiring, and control-board tests require a technician using the Hi-Ultra Xtreme 454B service procedure. | One restart after a fully thawed cooling coil may establish recurrence; do not cycle a heating overload or a returning protection code repeatedly. | mixed-primary-sources | Hisense HVAC | 2026-09-03 | https://hvac-bench.com/brands/hisense/hi-ultra-xtreme-code-16/ |
brands/hisense/sensor-error-codes | Hisense | hisense | Sensor group | ductless-mini-split | Hisense residential split air conditioners documented in the Hisense service and document library | Hisense Hi Ultra; Hisense Hi Ultra Xtreme; Hisense Energy series | temperature-sensor-fault | Hisense sensor codes: when the number identifies a reading, not a part | Hisense sensing codes report that a temperature reading has left the range the control will act on. Every one of them describes a measurement rather than a component, which is why the same code covers a failed element, a disconnected plug, and a corroded terminal without distinguishing between them. | Hisense publishes documentation by product family rather than as one brand-wide list, and code assignments differ between the residential ranges. The service document for the model on your data plate is the reference; a table gathered from another Hisense product may not transfer. | Photograph the indoor display showing the code before interrupting power for any reason. | Compare the temperature the unit reports with a thermometer and write both figures down. | Note any storm, flooding, pest activity, or outdoor work in the weeks before the fault appeared. | Measuring sensing resistance and inspecting connectors requires the indoor or outdoor casing to be opened, and the outdoor enclosure carries mains voltage as well as refrigerant pipework. | Do not attempt to dry, clean, or reseat an outdoor connector. Water ingress often accompanies damage that is not visible from outs... | The measurement is taken again as soon as the equipment powers up, so a reset changes nothing while the reading is out of range. It does, however, erase the displayed code, so photograph it first. | mixed-primary-sources | Hisense HVAC | 2026-09-15 | https://hvac-bench.com/brands/hisense/sensor-error-codes/ |
brands/hitachi/yutaki-alarm-70 | Hitachi | hitachi | 70 | heat-pump | Yutaki hydronic heat-pump systems | Yutaki systems covered by Hitachi alarm 70 guidance | water-flow-fault | Hitachi Yutaki alarm 70: no water flow detected | Hitachi's Yutaki technical guidance ties alarm 70 to an unsuccessful water-flow check. The alarm does not prove that the circulation pump failed: a blocked hydraulic route, closed valve, clogged filter, air, low water condition, pump problem, or flow detection issue can all prevent confirmed circulation. | This definition is limited to Hitachi Yutaki heating systems covered by the cited manufacturer technical tip. A two-digit Hitachi alarm on an air-conditioning or Set Free controller may have a different scope. | Record the alarm, model, requested mode, visible controller pressure, recent hydraulic work, and external leakage without opening the appliance. | Flow measurement, pump tests, filter access, air removal, valve diagnosis, and electrical sensing checks require the Yutaki installer or service engineer. | Avoid repeated resets of alarm 70 because an unresolved no-flow condition can continue; follow the user manual and preserve recurrence details. | oem-support | Hitachi Cooling and Heating | 2026-09-03 | https://hvac-bench.com/brands/hitachi/yutaki-alarm-70/ |
brands/hitachi/yutaki-alarm-77-78 | Hitachi | hitachi | 77 / 78 | controls-thermostats | ATW-RTU room thermostats paired with ATW-IOT-01 on Yutaki systems | ATW-RTU-12 wireless room thermostat; ATW-IOT-01 interface; Yutaki systems using the ATW-RTU controls | wireless-link-alarm | Hitachi Yutaki alarms 77 and 78: the radio link, not the heat pump | Both alarms are about communication rather than heating. Alarm 77 means the Yutaki unit has lost communication with the ATW-IOT-01 interface, and alarm 78 means communication between ATW-IOT-01 and the ATW-RTU-12 thermostat has failed. | These alarm numbers belong to the ATW-RTU room thermostat and the ATW-IOT-01 interface on Yutaki systems, as published in the Hitachi installation and operation manual for those controls. Yutaki units raise their own alarms in their own numbering, and a number seen on a wired controller is not necessarily the same numb... | Record the alarm exactly, including any decimal, and note which display you read it on. | Confirm the ATW-IOT-01 interface is powered, which is the first check the manual lists for both alarms. | Note whether anything changed in the property recently, such as a new appliance, a partition, or a repositioned thermostat. | Wiring integrity, wire loops, and interference sources on the Yutaki to interface link are installer work rather than owner checks. | A repeating alarm 78.1 is assigned to the room thermostat hardware and the manufacturer response is replacement, which should be arranged rather than attempted. | A link alarm clears when the link recovers, so the useful measure is whether it stays cleared rather than whether it can be dismissed. Record each occurrence instead of clearing and forgetting it. | mixed-primary-sources | Hitachi Cooling and Heating | 2026-09-03 | https://hvac-bench.com/brands/hitachi/yutaki-alarm-77-78/ |
brands/hitachi/yutaki-alarm-code-groups | Hitachi | hitachi | Alarm groups | heat-pump | Hitachi Yutaki air-to-water heat pump systems documented in the Hitachi air-to-water installation and operation manuals | Yutaki S; Yutaki S Combi; Yutaki M; Yutaki S80 | protection-shutdown | Hitachi Yutaki alarms: the water side and the refrigerant side are different jobs | A Yutaki system has two fluid circuits that can each raise alarms: a refrigerant circuit between the outdoor unit and the heat exchanger, and a water circuit serving the house. Knowing which side an alarm belongs to decides almost everything that follows, including whether the work is certified refrigerant handling or ... | Yutaki covers split, monobloc, and high-temperature configurations, and the alarm set differs between them as well as between generations of the controller. Read the alarm against the installation and operation manual for your exact configuration rather than a general Hitachi list. | Photograph the controller showing the alarm number and any accompanying text before anyone resets it. | Record the outdoor temperature, the flow temperature the controller was asking for, and whether hot water is also affected. | Check the system pressure on the heating circuit and note the reading while the system is ... | Any alarm belonging to the refrigerant circuit requires a certified refrigerant handler under F-Gas rules in the United Kingdom and European Union, or EPA Section 608 in the United States. | Water-side work on a heat pump, including pump settings and circuit balancing, should be carried out by an engineer familiar with... | Clearing an alarm allows the system to try again, and where the condition is seasonal it may run for days before repeating. Record the alarm and the conditions before resetting, since the pattern is what identifies a marginal design. | mixed-primary-sources | Hitachi Cooling and Heating | 2026-09-15 | https://hvac-bench.com/brands/hitachi/yutaki-alarm-code-groups/ |
brands/hive/boiler-not-responding-to-hive | Hive | hive | No signal / offline | controls-thermostats | Hive heating control systems using a hub, a thermostat, and a boiler receiver as described in Hive support | Hive Active Heating; Hive Thermostat Mini; Hive Hub and receiver | communication-fault | Hive not controlling the boiler: three links that can break separately | A Hive installation is a chain: the app talks to Hive, Hive talks to the hub, the hub talks to the thermostat and the receiver, and the receiver switches the boiler. A break anywhere along that chain presents in the app as the heating not responding, and the repair depends entirely on where the break is. | Hive has shipped several generations of hub, thermostat, and receiver with different radio arrangements and different indications. The Hive support material for the products you actually own is the reference, and the position of a break is established from the devices rather than from the app alone. | Operate the manual or boost control on the receiver and note whether the boiler responds, which splits the fault in half immediately. | Check whether the thermostat still controls the heating locally even if the app cannot reach the system. | Note anything that changed in the house recently: a new router, a moved hub, ... | Wiring between a receiver and a heating appliance carries mains voltage on United Kingdom installations and is not an owner task. | A boiler that does not respond to manual operation at the receiver is a heating fault rather than a connectivity one, and it belongs to a Gas Safe registered engineer. | Restarting the hub and the router restores an internet or account link and does nothing for a radio or wiring break. Establish where the break is with the receiver test before restarting anything. | oem-support | Hive Home; Hive | 2026-09-15 | https://hvac-bench.com/brands/hive/boiler-not-responding-to-hive/ |
brands/honeywell-home/t6-not-calling-for-heat | Honeywell Home | honeywell-home | No heat demand | controls-thermostats | Honeywell Home T6 programmable thermostats configured through installer setup parameters | T6 Pro; T6 Pro Smart; Lyric T6; T6R wireless | communication-fault | Honeywell T6 not calling for heat: installer settings before faults | A Honeywell T6 that shows a set point above the room temperature and still produces no heat is either being prevented by a configuration parameter or is not connected to what it thinks it is. Installer setup decides system type, staging, changeover, and minimum off times, and each of those can suppress a demand that lo... | T6 covers wired and wireless variants across several markets, with installer setup parameters that differ between them. The installer setup guide for the exact T6 variant you own is the reference, and a parameter number from a different variant can select something else entirely. | Confirm the time, the day, and the schedule on the thermostat, and check whether a hold or a temporary override is active. | Raise the set point by hand and note whether heat arrives, which separates scheduling from everything downstream. | On a wireless variant, look at the receiver near the appliance and note whether... | Installer setup parameters govern which terminals are energised and how equipment is staged, and selecting the wrong system type can make a thermostat energise a circuit the equipment does not expect. | Terminals inside a boiler or a wireless receiver sit at mains potential in British installations, which puts any work... | Restarting the thermostat clears a temporary state and leaves installer parameters exactly as they were. Where configuration is the cause, only the setup menu changes it. | oem-operation-manual | Honeywell Home | 2026-09-15 | https://hvac-bench.com/brands/honeywell-home/t6-not-calling-for-heat/ |
brands/ideal-heating/logic-f1-low-pressure | Ideal Heating | ideal-heating | F1 | boiler | Ideal Logic, Logic Max, and Logic Plus boilers that display F1 | Logic Combi; Logic Max Combi; Logic Max System; Logic Plus | low-water-pressure | Ideal Logic F1 fault code: what low water pressure means | Ideal defines F1 as low water pressure in the sealed heating system, and the boiler stops until the pressure is raised. Ideal tells the owner to check the gauge reads between 1 and 1.5 bar and to repressurise with the filling loop if it is low, then to call a Gas Safe registered engineer if the pressure keeps dropping. | This applies to Ideal Logic family boilers whose published fault guidance lists F1. Ideal uses L1 for a flow overheat or no-flow condition, which is a different branch, so read the exact characters on the display before acting. | With the boiler off and cool, read the pressure gauge and top up to about 1.5 bar with the filling loop only if it is below 1 bar. | After topping up, close both filling-loop valves fully and check whether the pressure holds over the next day of normal heating. | A pressure that will not hold, visible leaks or staining, an expansion vessel check, or an F1 that alternates with L1 needs a Gas Safe registered engineer. | Reset once after a successful top-up to 1.5 bar. Ideal notes a separate lockout for resetting too many times in fifteen minutes, so do not cycle the reset while F1 persists. | mixed-primary-sources | Ideal Heating | 2026-09-09 | https://hvac-bench.com/brands/ideal-heating/logic-f1-low-pressure/ |
brands/ideal-heating/logic-f2-flame-loss | Ideal Heating | ideal-heating | F2 | boiler | Ideal Logic and Vogue gas boilers using the F-series and L-series fault codes published by Ideal Heating | Logic Combi; Logic Max Combi; Logic System; Vogue Max | flame-loss | Ideal F2: the flame was there and then it was not | Ideal uses F2 for a flame loss condition, which is a different event from a failure to establish flame at all. The burner lit, ran, and then the appliance stopped detecting combustion, so the investigation starts from what changed during operation rather than from what prevented ignition. | Ideal publishes separate fault code lists for its Logic, Logic Max, and Vogue ranges, and the same character can carry different detail across them. Take the code from the display of the appliance in front of you and check it against the Ideal literature for that model rather than a general list. | Time how long the boiler runs before the fault appears, and note whether heating or hot water was actually produced. | Record which other gas appliances were in use each time the fault occurred. | Note whether failures happen on small demands, large demands, or both, since the pattern is diagnostic. | Measuring working gas pressure, testing the flame signal, and inspecting the flue and condensate arrangement are Gas Safe registered tasks. | If gas can be smelled, that single fact outranks the fault code entirely. Get everyone out, touch no switches, and telephone the emergency line for your supplier once you are out... | Ideal permits a reset from the control panel, and a small number of attempts establish whether the fault repeats and at what point. Continuing beyond that adds ignition cycles without adding information. | mixed-primary-sources | Ideal Heating | 2026-09-15 | https://hvac-bench.com/brands/ideal-heating/logic-f2-flame-loss/ |
brands/ideal-heating/logic-l1-and-l3-water-flow | Ideal Heating | ideal-heating | L1 | boiler | Ideal Logic and Logic Max boilers covered by the published fault code guidance | Ideal Logic Combi; Ideal Logic Max Combi; Ideal Logic System; Ideal Logic Heat | boiler-circulation-fault | Ideal L1 and L3: overheat and no water flow are not the same fault | Ideal publishes L1 as flow temperature overheat or no water flow and L3 as no water flow. For L1, Ideal says to open all radiator valves, confirm 1 to 1.5 bar, and reset. Its L3 guidance includes checking pressure and bleeding air from radiators. Record the exact code because the published wording and checks are not id... | These are Ideal Heating's published codes for its Logic and Logic Max ranges. Ideal also publishes an F-series in parallel, so an F1 on the same appliance is low pressure rather than an overheat. A letter and a number read from another manufacturer's boiler carries no relationship to these definitions. | Walk the house and open user-operated radiator valves and thermostatic heads; do not alter lockshield balancing valves. | Read the pressure gauge cold and top up to the 1 to 1.5 bar band Ideal names if it is low. | Bleed radiators that are cold at the top, then recheck the pressure afterwards. | Reset the boiler once a... | L1 or L3 returning after every valve is open, the pressure is correct, and the radiators have been bled. | An L5 code, which indicates the boiler has been reset too many times rather than diagnosing the original fault. | Any suspicion of a circulation pump fault or a blocked circuit, both of which need the casing opene... | Ideal's L1 and L3 guidance ends each check with a reset, and its L5 code defines the limit: too many resets within fifteen minutes produces its own lockout, cleared by power cycling. One reset per corrective action, with a full heating cycle observed afterwards, stays inside that boundary. | oem-support | Ideal Heating | 2026-09-08 | https://hvac-bench.com/brands/ideal-heating/logic-l1-and-l3-water-flow/ |
brands/ideal-heating/logic-max-l2-fault | Ideal Heating | ideal-heating | L2 | boiler | Logic Max Combi boilers in manual 237660 A01 | Logic Max Combi 2 C24; Logic Max Combi 2 C30; Logic Max Combi 2 C35 | flame-loss-lockout | Ideal Logic Max L2 flame-loss lockout | On the documented Ideal Logic Max Combi, L2 is a flame-loss lockout. It records failure to establish or retain valid flame through the supervised sequence; it does not prove a dirty electrode. Gas pressure, valve command, spark, electrode and lead, condensate, flue, flame signal, and control require qualified tests. | This L2 interpretation is limited to Logic Max Combi models covered by Ideal manual 237660 A01. Vogue, older Logic, Logic Air, and commercial Ideal appliances use their own fault tables. | Save L2, the model, other gas-appliance status, and audible startup sequence from outside the sealed case without forcing repeated ignition. | Gas pressure, valve, spark, electrode, flame-current, combustion, flue, condensate, wiring, and sealed-case work require a Gas Safe registered engineer. | Use at most one reset allowed by the exact user instructions; a remaining or returning L2 must not be reset repeatedly. | mixed-primary-sources | Ideal Heating | 2026-09-03 | https://hvac-bench.com/brands/ideal-heating/logic-max-l2-fault/ |
brands/klimaire/ksiv-e1-error-code | Klimaire | klimaire | E1 | ductless-mini-split | KSIV Series | KSIV Series systems covered by Klimaire troubleshooting manual 245 | communication-fault | Klimaire KSIV E1 indoor-outdoor communication error | Klimaire's KSIV troubleshooting literature defines E1 as an indoor-to-outdoor communication error. The code covers the complete path, including terminal order, installed cable, electrical supply, and the transmitting and receiving circuits; it does not independently diagnose a control board. | Use this meaning only for Klimaire KSIV systems within the cited service literature. KSIA, KDIP, and other Klimaire platforms can use different diagnostic tables even when an indoor display looks similar. | Capture E1, both complete model labels, first-occurrence timing, and any externally visible cable damage without opening an electrical panel. | Terminal inspection, cable testing, supply verification, signal measurement, and control-board diagnosis require a qualified KSIV technician. | Limit resetting to one KSIV-approved power cycle; when E1 returns, leave the communication path available for diagnosis. | mixed-primary-sources | Klimaire | 2026-09-03 | https://hvac-bench.com/brands/klimaire/ksiv-e1-error-code/ |
brands/klimaire/indoor-and-outdoor-code-split | Klimaire | klimaire | Indoor and outdoor groups | ductless-mini-split | Klimaire ductless mini-split systems documented in the Klimaire service and support library | KSIV series; KSIO series; Klimaire multi-zone indoor units | communication-fault | Klimaire codes: which half of the system is speaking | Klimaire documents its codes in groups that separate indoor conditions from outdoor ones, and that split is the first thing to use. Knowing which half raised the condition tells you where a technician will work and what class of repair is likely, before any exact entry has been found. | Klimaire publishes service documentation per series, and the KSIV and KSIO lines carry their own tables. The document matching the model number on the data plate is the mapping, and a chart labelled with the brand alone can describe a different series. | Photograph the displayed code and both data plates before contacting anybody or interrupting power. | Note whether the outdoor unit runs at all, which is observable from a safe distance and separates the two groups immediately. | Record whether the fault has been present since installation or developed after a period o... | Outdoor-side conditions involve the sealed refrigerant circuit and the drive, both of which require certification and the appropriate instruments. | Indoor casings carry the supply to the board and the fan motor, so opening one is qualified work even where the component behind the code is small. | A single power interruption separates a latched report from a live condition, and on this equipment it also tells you whether the outdoor unit attempts to start. Capture the code before doing it. | mixed-primary-sources | Klimaire | 2026-09-15 | https://hvac-bench.com/brands/klimaire/indoor-and-outdoor-code-split/ |
brands/klimaire/p4-inverter-drive-error | Klimaire | klimaire | P4 | ductless-mini-split | KSIO series systems in the manufacturer troubleshooting manual | KSIO009-H124-I; KSIO012-H123-I | inverter-drive-error | Klimaire P4: one indoor code, three outdoor LED patterns | P4 is an inverter compressor drive error. On the documented KSIO models the outdoor board publishes three different green and red LED combinations that all display as P4 indoors, so the outdoor board is carrying detail the indoor display does not. | The LED table here is published for KSIO009-H124-I and KSIO012-H123-I in the Klimaire troubleshooting manual. Klimaire documents its series separately, and the KSIA, KSIV, and KDIP families each have their own tables, so confirm the model on the outdoor plate before using this page. | Photograph the indoor display showing P4, and note the time and the mode the system was in. | Observe the outdoor indicator lamps from outside the cabinet and record which are lit or flashing. | Record the outdoor model number from the data plate, since the LED table is published per model. | The manual states it is for use by a certified service technician and warns that capacitors hold charge after the supply is switched off. | Drive diagnosis, module testing, and compressor measurement all require the cabinet open with the bus discharged, which is technician work. | One power interruption establishes whether P4 survives it. Repeating that on a drive error asks the same conversion to be attempted again, so record the outcome of the first attempt and stop. | mixed-primary-sources | Klimaire | 2026-09-03 | https://hvac-bench.com/brands/klimaire/p4-inverter-drive-error/ |
brands/lennox/icomfort-alerts-10-31-39 | Lennox | lennox | 10, 31, 39 | controls-thermostats | Lennox communicating systems on iComfort S30, E30 and compatible displays, covering furnaces, air handlers, outdoor units, equipment interface modules and iHarmony zoning | Lennox iComfort S30 and E30 communicating thermostats; Lennox communicating furnaces, air handlers and outdoor units on the same bus; Lennox iHarmony damper control module and equipment interface module | intermittent-communication | Lennox iComfort alerts 10, 31 and 39 that keep coming back: tracing intermittent faults without swapping parts | Only one of the three is a communication code. Alert 31 reports that a component has not communicated with the thermostat for more than three minutes, and Lennox documents it as clearing once communication is restored. Alert 10 reports that an unknown device was found on the bus and needs configuring, not repairing. Al... | These entries come from the Lennox residential communicating systems alert table used with iComfort S30 and E30 displays. Lennox equipment running on a conventional 24 volt thermostat does not use this table, and legacy control-board flash patterns on the same appliance carry unrelated meanings. | Record the date, time and outdoor conditions each time an alert appears, and keep the list rather than clearing it. | Look for standing water or a slow drain at the indoor unit, because a float switch in series with the R terminal interrupts communication when it lifts. | Photograph any seven-segment display on the equ... | Voltage and continuity measurement at a communicating control is energised low-voltage work for a qualified technician. | Reconfiguration through the installer control center, and any isolation of devices on the bus one at a time, belongs to the installing contractor. | Lennox documents a power cycle only if alert 31 persists. Cycling power on a fault that has already self-cleared removes the timestamps that make an intermittent pattern visible. | oem-service-manual | Lennox | 2026-09-04 | https://hvac-bench.com/brands/lennox/icomfort-alerts-10-31-39/ |
brands/lennox/xp17-icomfort-alert-411 | Lennox | lennox | 411 | heat-pump | XP17 heat pumps with iComfort communicating controls | XP17-024; XP17-030; XP17-036; XP17-042; XP17-048; XP17-060 | low-pressure-lockout | Lennox XP17 iComfort Critical Alert 411 | For the Lennox XP17, Critical Alert 411 records repeated low-pressure-switch events that reached a lockout threshold. It does not prove low refrigerant charge: airflow, outdoor conditions, restriction, switch or wiring faults, and the refrigerant circuit all require operating measurements. | This meaning follows the XP17 installation and service procedure cited here. Lennox alert numbers depend on the communicating equipment and control generation, so confirm the outdoor model and alert text together. | Save the complete iComfort alert history, operating mode, filter condition, weather, visible outdoor clearance, and recent service without opening equipment. | Pressure-switch, wiring, refrigerant, airflow commissioning, control-log, and live electrical diagnosis require a Lennox-qualified technician. | Do not repeatedly clear a critical 411 lockout; preserve its history and allow service to test the conditions that opened the protection. | mixed-primary-sources | Lennox | 2026-09-03 | https://hvac-bench.com/brands/lennox/xp17-icomfort-alert-411/ |
brands/lennox/xp17-alert-418-419 | Lennox | lennox | 418 / 419 | heat-pump | XP17 heat pumps with iComfort communicating controls | XP17-024; XP17-030; XP17-036; XP17-042; XP17-048; XP17-060 | control-input-fault | Lennox XP17 alerts 418 and 419: a W input fault or a miswire | Alert 418 is raised when the heat pump control sees the W output active while a compressor demand is running, which the installation manual describes as a W input fault or a miswire. Five occurrences within a single demand escalate it to a hardware fault lockout and alert 419. | These alert numbers and the strike behaviour come from the Lennox XP17 installation and service procedure for the models listed. Lennox uses the same numbering family across several iComfort products, and the sequence a given alert follows belongs to the equipment it was published for. | Record the alert number, whether it was 418 or 419, and whether the system was still heating when it appeared. | Note any thermostat replacement, system conversion, or wiring work carried out before the alert started. | Note whether the property has a backup or auxiliary heat source and how it is meant to be controlled... | Low voltage wiring, thermostat configuration, and the field test pins are all inside equipment covers and belong to a qualified technician. | Ask for the wiring and the thermostat configuration to be verified before any part is quoted, since the manual attributes this alert to an input fault or a miswire. | Clearing the lockout restores operation without changing the condition that produced it. If 418 returns after a reset, the wiring or the configuration is still telling the control the same contradictory thing. | mixed-primary-sources | Lennox | 2026-09-03 | https://hvac-bench.com/brands/lennox/xp17-alert-418-419/ |
brands/lennox/icomfort-control-restarting | Lennox | lennox | Control restart | controls-thermostats | Lennox iComfort communicating thermostats and the equipment controls they are paired with | iComfort S30; iComfort E30; iComfort M30; iComfort Wi-Fi | communication-fault | Lennox iComfort keeps restarting: separating a control reboot from an equipment fault | A Lennox iComfort control that restarts on its own is describing its own operating conditions rather than a heating or cooling fault. What the control needs is a stable supply from the equipment to stay running, and a supply that dips, a loose conductor, or a software condition can all produce a reboot that looks alarm... | This covers Lennox iComfort communicating controls paired with compatible Lennox equipment. A Lennox system using a conventional thermostat behaves differently, and a restart on a non-Lennox control fitted to Lennox equipment is outside what Lennox documents. Identify the control model from its own settings menu. | Keep a short log of each restart with the time and what the heating or cooling system was doing in that moment. | Note which settings survive a restart and which have to be entered again. | Check whether any recent electrical work, network change, or equipment service preceded the behaviour. | Inspecting control wiring at the equipment, measuring supply under load, and updating control firmware are dealer tasks on a communicating system. | Do not add or move conductors at the control or the equipment to try to stabilise the supply. Communicating systems use those conductors for data as well as power. | The control restarting is itself a reset, so performing another one adds nothing. What matters is whether the restarts are synchronised with equipment starting, which only observation over time can establish. | mixed-primary-sources | Lennox | 2026-09-15 | https://hvac-bench.com/brands/lennox/icomfort-control-restarting/ |
brands/lg/ch01-ch02-ch06-ch12-sensor-codes | LG | lg | CH01 / CH02 / CH06 / CH12 | ductless-mini-split | LG residential air conditioners covered by the United States help-library article that groups these codes as sensor problems | LG single-split wall units; LG multi-split indoor units; LG art cool wall units | temperature-sensor-fault | LG CH01, CH02, CH06 and CH12: the codes LG calls a sensor problem | LG's own help-library article does not give these codes one meaning each. It places CH01, CH02, CH06, CH12, the CH41 to CH48 range, E1 to E3, E7, E8, F2 and F3 in a single category described as a problem with a sensor. The practical consequence is that the code identifies which sensing input is unhappy, while LG's publ... | The grouping quoted here is LG's United States help-library guidance for residential air conditioners. LG multi-split and commercial equipment publish fuller per-code tables in their service literature, and LG documentation varies by region and by generation, so a code on a commercial LG system is read from that system... | Write the code down exactly as shown, since a zero and a letter O are easy to confuse on a small indoor display. | Carry out the single power interruption LG describes, at the plug or the breaker, and wait about five minutes before restoring supply. | Compare the displayed room temperature with a separate thermometer a... | LG instructs the owner not to disassemble the air conditioner or replace internal parts, and warns that doing so may cause fire, electric shock, or serious injury. | If the same code appears again after one reset, LG's stated instruction is to stop using the product and request service to prevent further damage. | LG permits exactly one interruption of about five minutes at the plug or the breaker. Repeating it after the code returns is contrary to LG's own published instruction to stop using the product. | oem-support | LG Electronics | 2026-09-15 | https://hvac-bench.com/brands/lg/ch01-ch02-ch06-ch12-sensor-codes/ |
brands/lg/ch04-error-code | LG | lg | CH04 | ductless-mini-split | LG single-zone systems in general service manual MFL41161610 | LG single-zone indoor units covered by General Service Manual MFL41161610 | drain-circuit-fault | LG CH04: float switch error, or a missing jumper | CH04 reports the float switch circuit rather than a measured water level. On an indoor unit fitted with a float switch it points at drainage or the switch; on a model built without one it follows a short key missing from the float switch connector on the indoor board. | Whether your indoor unit has a float switch at all decides which half of this code applies, and that depends on the cabinet style and the exact model. Establishing it is the first thing document MFL41161610 asks a technician to do, which is why the characters alone cannot answer CH04 on any single-zone LG system. | Note whether water has appeared at or under the indoor unit, and whether the outside drain discharges during cooling. | Record the indoor model number, since whether a float switch is fitted at all depends on it. | Note any recent work at the indoor unit, particularly a board replacement or a service visit that opened ... | The float switch connector, the short key, and the indoor board sit inside the electrical compartment and are technician work with the supply isolated. | Ask for the short key test described in the manual before an indoor board is quoted, because the manual conditions that replacement on it. | A restart tells you whether the circuit reads open again as soon as the board looks at it. Repeating it does not close a drain or refit a short key, so one attempt is the useful limit. | mixed-primary-sources | LG Electronics | 2026-09-03 | https://hvac-bench.com/brands/lg/ch04-error-code/ |
brands/lg/ch05-error-code | LG | lg | CH05 | ductless-mini-split | LG single-zone systems in MFL41161610 | LG single-zone systems covered by General Service Manual MFL41161610 | communication-fault | LG CH05 error code: indoor-outdoor communication error | LG's documented CH05 code indicates an indoor-to-outdoor communication error; the same service table groups related CH53 and CH93 communication conditions by system context. | This page follows the LG general service manual for single-zone ductless systems. LG multi-zone and ducted ranges maintain their own code tables, and a CH number read from a different manual is not interchangeable, so confirm the model against the manual before relying on this definition. | Record the complete code, model numbers, and whether either unit shows signs of power. | Note whether the code followed an outage, installation, or other electrical work without opening a panel. | Terminal, grounding, resistance, motor, and PCB checks in the service manual require a qualified technician. | Wait-time and stored-energy warnings in the service literature must be followed before electrical access. | A controlled power cycle can document recurrence; continuing CH05 should be diagnosed rather than repeatedly cleared. | oem-service-manual | LG Electronics | 2026-09-02 | https://hvac-bench.com/brands/lg/ch05-error-code/ |
brands/lg/ch07-operating-mode-conflict | LG | lg | CH07 | multi-zone | LG multi-split systems where several indoor units share one outdoor unit | LG Multi F; LG Multi F Max; Art Cool multi-zone heads; ceiling cassette multi-zone heads | operating-mode-conflict | LG CH07 error code: indoor units set to conflicting modes | LG shows CH07 on a multi-split when the indoor units connected to one outdoor unit are set to modes that cannot run at the same time, such as one head in heating and another in cooling or dehumidification. It is a setting conflict, not a hardware fault, and it clears when every head is set to a compatible mode. | This applies to LG multi-split systems where more than one indoor unit shares a single outdoor unit. A single-split system with one indoor and one outdoor unit does not produce CH07 for this reason, so confirm the system is a multi-split first. | Check the mode shown on every indoor remote for units sharing the outdoor unit, and set them all to heating or all to cooling. | After the modes match, turn the affected heads off and on again and confirm CH07 has cleared. | If CH07 stays after every head is confirmed on the same mode, a wired controller or communication fault may be reporting a mode incorrectly, which needs an LG technician. | Turning the heads off and on after matching their modes is the reset. If CH07 returns with every head confirmed on one mode, stop and have the controllers checked. | oem-support | LG Electronics | 2026-09-09 | https://hvac-bench.com/brands/lg/ch07-operating-mode-conflict/ |
brands/lg/ch21-ch23-ch26-ch29-compressor-codes | LG | lg | CH21 / CH23 / CH26 / CH29 | heat-pump | LG residential air conditioners covered by the United States help-library article grouping these codes as outdoor compressor or circuit board problems | LG single-split outdoor units; LG multi-split outdoor units; LG inverter heat pump outdoor units | inverter-module-protection | LG CH21, CH23, CH26 and CH29: the outdoor compressor and board group | LG's help-library article assigns CH21, CH23, CH26, CH29 and E9 to a single category: a problem with the outdoor unit compressor or circuit board. That is a narrower statement than it appears, because it moves the fault out of the indoor unit and out of the sensing group and places it in the inverter drive and compress... | What is quoted below is the category LG gives home customers in its United States help library, and nothing finer. LG service literature publishes fuller definitions for each of these codes, and the meaning of a CH number on LG commercial or variable refrigerant flow equipment is taken from that product's own manual ra... | Make one start attempt after LG's five-minute power interruption, and count how many seconds the outdoor unit runs before it stops. | Observe whether the outdoor fan turns at all during the attempt, from a safe distance and without touching the guard. | See whether a breaker or fuse serving the outdoor unit has tripped... | LG instructs the owner not to disassemble the unit or replace internal parts, warning of fire, electric shock, serious injury, or death. | Measuring compressor windings, inverter output, and supply voltage under load are energised tasks inside the outdoor enclosure and belong to a qualified engineer. | One interruption of about five minutes is what LG publishes. Because this group covers an electrical protection, repeating it after the code returns risks converting a diagnosable fault into a replacement. | mixed-primary-sources | LG Electronics | 2026-09-15 | https://hvac-bench.com/brands/lg/ch21-ch23-ch26-ch29-compressor-codes/ |
brands/lg/multi-split-mode-conflict | LG | lg | Mode conflict | multi-zone | LG multi-split systems where several indoor units share a single outdoor unit, as described in LG help-library guidance | LG multi-split outdoor units; LG multi-split wall indoor units; LG multi-split ducted indoor units | not-heating | LG multi-split: one outdoor unit cannot heat and cool at once | LG states that on a multi-product system every indoor unit connected to one outdoor unit has to run in cooling only or in heating only. Cooling and dehumidification cannot run at the same time as heating, while air purification and fan modes are unrestricted, so one room set the wrong way stops another from getting wha... | This applies to LG multi-split arrangements where several indoor units share one outdoor unit. Heat recovery systems, which are a different architecture, can serve simultaneous heating and cooling, and single-split installations have no conflict to resolve. Confirm how many indoor units your outdoor unit serves. | Walk through every room with an indoor unit and note which mode each one is set to, including any that are switched on but unused. | Switch off indoor units in rooms nobody is using rather than leaving them running in a conflicting mode. | Set every remaining unit explicitly to the same mode rather than relying on auto... | A conflict that persists after every indoor unit is set to the same mode is no longer a mode conflict and needs the system examined. | Changing how a multi-split is configured, including adding or reassigning indoor units, is installer work rather than a settings change. | Nothing needs resetting for a mode conflict, because nothing has faulted. Operation resumes as soon as the requests agree, which is why setting every unit to one mode is the test as well as the fix. | oem-support | LG Electronics | 2026-09-15 | https://hvac-bench.com/brands/lg/multi-split-mode-conflict/ |
brands/midea/e1-error-code | Midea | midea | E1 | ductless-mini-split | Aurora Xtreme Inverter 36,000 BTU cooling-only 220 V | Aurora Xtreme Inverter 36,000 BTU cooling-only 220 V documented model | communication-fault | Midea E1 error code: Aurora Xtreme communication fault | In the cited Midea Aurora Xtreme service manual, E1 means the indoor unit repeatedly failed to receive feedback from the outdoor unit; other Midea product categories can assign E1 differently. | This meaning belongs to one documented model: the Aurora Xtreme Inverter at 36,000 BTU, cooling only, 220 V. Midea builds across window units, portables, ducted equipment, and several ductless ranges, and E1 is not reserved for communication in all of them. If your model plate does not match, this page is the wrong pag... | Verify the exact model family before using this meaning, because Midea E1 is not universal. | Record whether the code appears after a power interruption or installation work. | Signal-voltage measurement, reactor inspection, and PCB replacement are technician procedures. | Do not open the outdoor electrical compartment or attempt live meter tests. | The cited service flow begins with a two-minute power-off restart; if E1 returns, stop at homeowner observations and obtain service. | oem-service-manual | Midea | 2026-09-02 | https://hvac-bench.com/brands/midea/e1-error-code/ |
brands/midea/e2-indoor-coil-sensor | Midea | midea | E2 | ductless-mini-split | Midea wall-split systems, and systems built on the same platform sold under other names, that publish E2 | Midea EVOX; Midea All Easy; Midea Xtreme Save; platform-partner wall units | temperature-sensor-fault | Midea E2 error code: indoor coil temperature sensor fault | Midea assigns E2 to a fault on the indoor coil temperature sensor, the thermistor clipped to the evaporator pipework. The control sees the sensor reading as an open circuit or a short circuit, so it stops relying on it. The fault is in the sensor, its wiring, or the board input, not in the coil itself. | This meaning follows Midea troubleshooting and service literature for wall-split systems that list E2 as the indoor coil or tube sensor fault. Midea supplies platforms to other brands with the same code table, and Midea's own portable and window units number codes differently, so confirm the model. | Note whether E2 is steady from every start or intermittent, and whether a power cycle clears it and for how long. | Record the indoor and outdoor model numbers so a technician can look up the correct sensor resistance table. | Measuring the sensor resistance, inspecting the harness and connector, and replacing the sensor or the board all require opening the indoor unit and belong with a technician. | A restart can show whether E2 is intermittent, which helps a technician. It does not repair a broken sensor or wire, so a returning E2 needs a meter rather than another reset. | mixed-primary-sources | Midea | 2026-09-09 | https://hvac-bench.com/brands/midea/e2-indoor-coil-sensor/ |
brands/midea/e3-indoor-fan-speed | Midea | midea | E3 | ductless-mini-split | Midea residential split air conditioners covered by the Midea online troubleshooting code reference | Midea Aurora series; Midea EVOX series; Midea Mission series | not-turning-on | Midea E3: the indoor fan is not running at the speed it was told to | Midea's code reference gives E3 as indoor fan speed out of control. The indoor board commands a speed and compares it against the rotation the motor actually reports, and a mismatch beyond what it tolerates raises the code. It says the speed is wrong; it does not say whether the motor, the drive, or something physical ... | Midea manufactures for many brands as well as selling under its own name, and code sets differ between those programmes even where hardware is shared. This reading applies to Midea-branded residential split equipment covered by the Midea troubleshooting reference. Confirm against the manual issued with your unit. | Switch the unit off rather than leaving it attempting to start, since the refrigerant circuit should not run against a stationary indoor coil. | Clean or replace the indoor filters according to the manual, and confirm the outlet louvres are free to move. | Capture a description of any sound that preceded the fault, whi... | Everything that would confirm this fault, from releasing a jammed wheel to putting a meter on the feedback line, happens with the indoor casing open and is therefore qualified work. | Do not reach through the outlet louvres to turn the fan wheel. The blades and the drive are not designed for that access and the assembl... | Power interruption clears the display and the board repeats the speed comparison on the next start. A code returning within seconds means the mechanical or electrical condition is unchanged. | mixed-primary-sources | Midea | 2026-09-15 | https://hvac-bench.com/brands/midea/e3-indoor-fan-speed/ |
brands/midea/p2-compressor-top-temperature | Midea | midea | P2 | heat-pump | Midea residential split air conditioners and heat pumps covered by the Midea online troubleshooting code reference | Midea Aurora series; Midea EVOX series; Midea multi-zone outdoor units | protection-shutdown | Midea P2: the compressor top temperature protection has acted | Midea gives P2 as compressor top temperature protection. A sensor on the compressor shell has reported a temperature above what the control permits, and operation has stopped to keep the motor and its lubricant inside their design range. It is a protection acting correctly, not a declaration that the compressor has fai... | Midea builds equipment for several brand programmes alongside its own range, and code assignments vary between them. This reading applies to Midea-branded residential split equipment covered by the Midea troubleshooting reference; a P2 on a unit sold under another name follows that brand's documentation. | Stop calling for operation and leave the system off so the compressor is not repeatedly restarted into the same condition. | Isolate the outdoor unit at its dedicated switch, then clear leaves, cuttings, and vegetation from around the casing without touching the coil fins. | Note the outdoor temperature at each stop an... | Charge measurement, leak detection, coil cleaning, and shell sensor testing are certified refrigerant and electrical tasks. | Never add refrigerant without finding where the previous charge went, and never wash or comb an outdoor coil without the training to avoid damaging the fins. | The protection re-evaluates the shell temperature on the next run, so a reset changes nothing while the condition persists. Repeated restarts add heat cycles the limit exists to prevent. | oem-support | Midea; Midea America | 2026-09-15 | https://hvac-bench.com/brands/midea/p2-compressor-top-temperature/ |
brands/mitsubishi/e6-communication-error | Mitsubishi Electric | mitsubishi | E6 | ductless-mini-split | Mitsubishi Electric M-Series and Mr Slim systems that publish the E-series communication table | MSZ-GL; MSZ-AP; MSZ-FH; MUZ paired outdoor units | communication-fault | Mitsubishi Electric E6 error code: indoor to outdoor communication fault | Mitsubishi Electric assigns E6 to a communication error between the indoor and outdoor units, detected on the indoor side. The two ends have stopped exchanging their signal over the connecting cable, so the code identifies a broken conversation rather than a specific failed board. | This meaning follows Mitsubishi Electric literature for the M-Series and Mr Slim families that publish an E-series table with E6 and E7. Mitsubishi Heavy Industries and other brands assign these characters differently, so confirm both model numbers before applying this page. | With the system off at the isolator, check for any obvious damage to the visible run of interconnecting cable and confirm no recent storm, outage, or rodent activity. | Record when E6 started, whether it followed any install or electrical work, and whether the outdoor fan turns while the code is shown. | Inspecting the S1, S2, S3 terminals, testing conductor continuity, and checking the board communication circuits all require isolating power and belong with a qualified technician. | Cycling the isolator once shows whether E6 clears on a restart. A code that comes straight back means the link is still down, and each extra reset only wipes timing a technician wants. | oem-support | Mitsubishi Electric; Mitsubishi Electric Trane HVAC US | 2026-09-09 | https://hvac-bench.com/brands/mitsubishi/e6-communication-error/ |
brands/mitsubishi/ecodan-l9-flow-rate | Mitsubishi Electric | mitsubishi | L9 | heat-pump | Ecodan FTC5 cylinder units, EHPT20X-MHCW and EHST20(D)(C)-MHCW | Ecodan EHPT20X-MHCW packaged cylinder units; Ecodan EHST20(D)(C)-MHCW split cylinder units; Packaged outdoor units PUHZ-W50 to PUHZ-HW140 and split outdoor units SUHZ-SW45 to PUMY-P140 | water-flow-fault | Ecodan L9: three different flow faults share one code | L9 means the control has measured low flow in a primary water circuit. The manual lists it three times for three circuits: heat source side sensed by the flow sensor, then Zone1 and Zone2, each sensed by a flow switch. The digit shown in Request code 569 under Running information tells you which of the three it is. It ... | Scoped to the FTC5 controller as documented in the EHPT20X-MHCW and EHST20(D)(C)-MHCW cylinder service manual. Later FTC generations and the newer Ecodan ranges carry their own code tables, and a code letter shared between two controllers is not a shared meaning. | Read the fault code and then look up Request code 569 in Running information on the main controller, and write down the digit shown. | Photograph the outdoor unit model number on the data plate, since the recommended flow range is per model. | Note the system pressure on the gauge and whether the pressure has been fall... | Strainer cleaning, purging a sealed system, and any work that breaks into the water circuit belong to the installer or a qualified heating engineer. | Electrical testing of the flow sensor, the flow switch, the CN1A connector, and the IN2, IN3, and IN7 terminals is technician work on a live control. | DIP switch settin... | null | mixed-primary-sources | Mitsubishi Electric | 2026-09-07 | https://hvac-bench.com/brands/mitsubishi/ecodan-l9-flow-rate/ |
brands/mitsubishi/p1-intake-air-thermistor | Mitsubishi Electric | mitsubishi | P1 | ductless-mini-split | Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment | MSZ-GL series; MSZ-FH series; PLA-A series; PKA-A series | temperature-sensor-fault | Mitsubishi P1: the room sensor the whole control loop depends on | P1 reports that the indoor intake air thermistor is reading outside the range the control accepts, which the reference describes as an open circuit, a short circuit, or a detached connector. The reading matters because the intake air sensor is what the system calls room temperature, so once it is untrusted the control ... | This reading covers Mitsubishi Electric indoor families that publish the P-series fault table. Mitsubishi Heavy Industries equipment is a separate manufacturer with its own table, and a P1 shown by a third-party controller wired to a Mitsubishi indoor unit is not the same entry. Confirm the indoor model code before act... | Compare the room temperature the controller displays with a separate thermometer placed near the indoor unit intake, and write both values down. | Confirm the front panel and filters are fully seated and closed, since a partly open panel changes what the intake sensor is exposed to. | Record the blink pattern or contro... | Measuring thermistor resistance, inspecting board connectors, and replacing a sensor harness require the indoor electrical enclosure to be opened by a qualified technician. | If P1 is accompanied by a burning smell, visible discoloration, or a tripping circuit protective device, isolate the unit and stop using it until... | Interrupting power clears the display but does not change a resistance that is out of range, so a P1 that returns after one restart is reporting a condition that is still present. | mixed-primary-sources | Mitsubishi Electric | 2026-09-15 | https://hvac-bench.com/brands/mitsubishi/p1-intake-air-thermistor/ |
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