ErrorLookupHub Appliance Diagnostics
Search Code

Appliance Error Codes Database

Found 168 verified diagnostic error codes

All Categories ductless-mini-split — Daikin 15 and 19 Series furnace — York YP9C modulating condensing gas furnaces documented in the York installation manual controls-thermostats — ATW-RTU room thermostats paired with ATW-IOT-01 on Yutaki systems ductless-mini-split — Gree residential mini-splits that publish E5 in the protection code family controls-thermostats — Bryant Evolution communicating systems using the Evolution Connex control and a four-conductor communication bus controls-thermostats — Google Nest Learning Thermostat and Nest Thermostat furnace — York Affinity YP9C modulating condensing furnaces and the TP9C, CP9C and LP9C models sharing the same installation manual boiler — Baxi and Potterton domestic boilers that display E119 controls-thermostats — Google Nest thermostats covered by the E-code power guide controls-thermostats — Google Nest learning and programmable thermostats that report power and delay conditions on screen ductless-mini-split — Mitsubishi Electric indoor units publishing the P-series fault table, including M-Series wall units and Mr Slim indoor equipment heat-pump — XP17 heat pumps with iComfort communicating controls ductless-mini-split — MRCOOL DIY mini-split generations that report an inverter compressor drive fault ductless-mini-split — Panasonic wall-mounted split systems that report H-series and F-series self-diagnosis codes heat-pump — Altherma 3 R MT with ELBH-E or ELBX-E and ERRA08-12 furnace — Rheem residential gas furnaces covered by the published technical FAQ furnace — R96V communicating condensing gas furnaces ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV indoor equipment ductless-mini-split — WindFree 3.0 AR C ductless-mini-split — Bosch Climate 5000 ductless mini-split systems documented in the Bosch service and manual library ductless-mini-split — BMKH floor-ceiling indoor units ductless-mini-split — Midea wall-split systems, and systems built on the same platform sold under other names, that publish E2 furnace — Goodman GMVC-series two-stage variable-speed gas furnaces documented in the installation and operating instructions ductless-mini-split — Diamante and Quantum systems in the manufacturer code list boiler — Vaillant ecoTEC gas boilers covered by the Vaillant United Kingdom fault code list ductless-mini-split — Mitsubishi Electric indoor units that publish the P-series protection table, including Mr Slim cassette, ducted, and ceiling-suspended indoor units heat-pump — LG residential air conditioners covered by the United States help-library article grouping these codes as outdoor compressor or circuit board problems ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction code chart, spanning room air, SkyAir, and VRV indoor equipment multi-zone — LG multi-split systems where several indoor units share a single outdoor unit, as described in LG help-library guidance ductless-mini-split — LG single-zone systems in MFL41161610 ductless-mini-split — Senville LETO Series ductless-mini-split — Diamante Essenza, Diamante Pro, Quantum Fresh, Hyperformance, and Ultra heat-pump — Stiebel Eltron WPL air source heat pumps commissioned through the manufacturer parameter set ductless-mini-split — Hisense residential split air conditioners documented in the Hisense service and document library boiler — Vaillant ecoTEC gas boilers covered by the published United Kingdom fault code list ductless-mini-split — Midea residential split air conditioners covered by the Midea online troubleshooting code reference heat-pump — Gree residential inverter systems covered by the OEM guide furnace — Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T ductless-mini-split — Della ductless mini-split systems documented in the Della manual and support library Dishwasher LaserJet Printer ductless-mini-split — Mr Slim families covered by Mitsubishi Electric's P8 reference ductless-mini-split — Multi21+ and documented residential mini-splits ductless-mini-split — Daikin multi-split systems and splits that publish UF for a wiring and piping combination fault boiler — Ideal Logic and Vogue gas boilers using the F-series and L-series fault codes published by Ideal Heating ductless-mini-split — Daikin split and multi-split systems that publish UA for an indoor and outdoor combination fault 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 ductless-mini-split — MRCOOL DIY ductless systems across the third, fourth, and fifth generations documented in MRCOOL support controls-thermostats — ecobee smart thermostats with installer settings governing staging, thresholds, and equipment lockouts controls-thermostats — Drayton Wiser multi-zone heating systems using a heat hub with room thermostats and smart radiator thermostats ductless-mini-split — MRCOOL single-zone and multi-zone families in official support ductless-mini-split — Gree residential mini-split indoor units using the F-series sensing bulb codes described in Gree North America support boiler — Ideal Logic, Logic Max, and Logic Plus boilers that display F1 Air Conditioner heat-pump — Mitsubishi Electric outdoor units publishing the U-series fault table, including M-Series and MXZ multi-zone outdoor equipment boiler — Ideal Logic and Logic Max boilers covered by the published fault code guidance ductless-mini-split — Econo IF, Vario TL, and Optima TP single zone, and the multi-zone systems sharing the table ductless-mini-split — Daikin room air conditioner splits and multi-split systems that publish U0 in the malfunction code table controls-thermostats — tado Smart Radiator Thermostat V3+ and earlier devices in the cited support flow ductless-mini-split — Panasonic room air conditioners with the self-diagnosis function described in Panasonic service documentation ductless-mini-split — LG single-zone systems in general service manual MFL41161610 ductless-mini-split — Sophia multi-zone cassette indoor units furnace — GMVC80 condensing gas furnaces boiler — Ariston Clas gas boilers whose fault codes are grouped by leading digit in the Ariston user documentation furnace — Carrier two-stage and variable-speed modulating condensing furnaces that report status code 31 furnace — Goodman and Amana gas furnaces with an integrated ignition control that flashes seven for low flame signal furnace — Affinity YP9C modulating gas furnaces boiler — Viessmann Vitodens gas condensing boilers whose displayed fault codes are listed in the Viessmann fault checker ductless-mini-split — Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment ducted-split — Carrier Infinity System Control paired with communicating equipment, with the outdoor-unit code structure documented for 24VNA6 and 25VNA4 variable-speed units heat-pump — Midea residential split air conditioners and heat pumps covered by the Midea online troubleshooting code reference ductless-mini-split — LG residential air conditioners covered by the United States help-library article that groups these codes as sensor problems boiler — Greenstar Si Compact ErP furnace — Ruud gas furnaces whose integrated controls report diagnostics through a blinking indicator, including the R96T range furnace — R96T two-stage communicating condensing furnaces controls-thermostats — Lennox iComfort communicating thermostats and the equipment controls they are paired with boiler — Worcester Bosch Greenstar boilers that pair E9 with cause code 219 ductless-mini-split — Samsung indoor air conditioner units whose display shows the reminder and operating-mode characters described in Samsung support ductless-mini-split — Econo, Vario, Optima, Motto, and Umbra mini-splits heat-pump — Hitachi Yutaki air-to-water heat pump systems documented in the Hitachi air-to-water installation and operation manuals heat-pump — NIBE air source and ground source heat pumps with controllers that store an alarm log and operating history boiler — Current ecoTEC plus boilers covered by manual 0020308121-04 ductless-mini-split — Pioneer Diamante and Quantum ductless systems whose code lists are published in Pioneer support ductless-mini-split — Panasonic reverse-cycle wall split systems that report F11 in the self-diagnosis table air-handler — Trane air handlers and indoor coils fitted with a condensate overflow switch, as described in Trane homeowner support boiler — Ariston Clas ONE, Clas System ONE, and Alteas ONE boilers showing 108 ductless-mini-split — KSIV Series ductless-mini-split — Senville ductless mini-split systems across the Aura, Leto, and earlier series documented in Senville support ductless-mini-split — Toshiba residential and light-commercial systems fitted with a wired remote controller controls-thermostats — Rheem and Ruud EcoNet communicating systems in which a smart thermostat or control center shares a four-wire network with indoor and outdoor equipment boiler — Logic Max Combi boilers in manual 237660 A01 ductless-mini-split — GE Zoneline packaged terminal air conditioners and heat pumps documented in GE Appliances owner and support material ductless-mini-split — Mitsubishi Heavy Industries room air conditioners documented in the MHI user manual library controls-thermostats — tado Smart Radiator Thermostat ductless-mini-split — Fujitsu General residential indoor units that report faults through operation and timer indicator lamps furnace — Trane gas furnaces whose integrated control proves flame by rectification, as described in Trane homeowner support for a burner that shuts off after ignition heat-pump — Yutaki hydronic heat-pump systems ductless-mini-split — Klimaire ductless mini-split systems documented in the Klimaire service and support library heat-pump — F2120 air-to-water heat pumps heat-pump — Daikin outdoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV outdoor equipment Washing Machine furnace — York YP9C, TP9C, CP9C, and LP9C furnaces covered by the cited manual ductless-mini-split — Mitsubishi Electric Mr Slim and M-Series systems that publish the P-series protection table multi-zone — LG multi-split systems where several indoor units share one outdoor unit controls-thermostats — tado smart thermostat systems using a wireless receiver or an extension kit between the control and the heating appliance ductless-mini-split — TCL residential split air conditioners documented in the TCL product download library ductless-mini-split — Hi-Ultra Xtreme R-454B furnace — Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, as covered by troubleshooting guide 58-3T heat-pump — Daikin outdoor equipment covered by the SM-TS3 malfunction chart, spanning room air, SkyAir, and VRV outdoor units ductless-mini-split — Mitsubishi Electric M-Series and Mr Slim systems that publish the E-series communication table ductless-mini-split — Forward Series systems in the manufacturer service manual boiler — Clas One and Clas System One condensing gas boilers ductless-mini-split — Climate 5000 Generation 3 R-454B multi-zone ductless-mini-split — KSIO series systems in the manufacturer troubleshooting manual furnace — Goodman and Amana single-stage and two-stage gas furnaces with an integrated ignition control boiler — Vaillant ecoTEC plus and ecoTEC sustain boilers that list F.22 ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems furnace — Rheem R96V modulating condensing gas furnaces documented in the Rheem service literature ductless-mini-split — Senville systems covered by the manufacturer EC 51 support article ductless-mini-split — Cooper and Hunter ductless mini-split systems documented in the Cooper and Hunter support library furnace — S9V2 S-Series two-stage condensing gas furnaces ductless-mini-split — Forward Series light-commercial — SkyAir RZR-P and RZQ-P(9) light-commercial — Amana PTAC models covered by the M70 service procedure ductless-mini-split — MRCOOL mini-splits covered by official P0/PC00 support furnace — Carrier 58MCB Series 110 and 120 condensing gas furnaces ductless-mini-split — LETO and AURA models using an applicable AC fan motor boiler — Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material ductless-mini-split — MRCOOL generations and models identified in official support furnace — Goodman GMVC80 condensing gas furnaces heat-pump — Grant Aerona air source heat pumps documented in the Grant fault and support material heat-pump — Ecodan FTC5 cylinder units, EHPT20X-MHCW and EHST20(D)(C)-MHCW boiler — Vitodens 100-W heat-only boilers in the cited UK installation instructions multi-zone — Climate 5000 Generation 3 R-454B multi-zone outdoor units heat-pump — Trane TruComfort variable-speed outdoor units on ComfortLink II communicating controls, including the XV20i heat pump ductless-mini-split — Amana packaged terminal air conditioners and heat pumps covered by the Amana PTAC service literature controls-thermostats — Honeywell Home T6 programmable thermostats configured through installer setup parameters controls-thermostats — Lennox communicating systems on iComfort S30, E30 and compatible displays, covering furnaces, air handlers, outdoor units, equipment interface modules and iHarmony zoning 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 furnace — Goodman GMVC-series and related integrated furnace controls documented in the installation and operating instructions heat-pump — Mitsubishi Electric inverter outdoor units publishing the U-series fault table, including M-Series single-zone and MXZ multi-zone equipment controls-thermostats — Hive heating control systems using a hub, a thermostat, and a boiler receiver as described in Hive support multi-zone — Multi21+ and the residential ranges in the Gree code overview ductless-mini-split — Discontinued Quantum WYS, CYB, RYB, UYB, and FYB heat-pump — Daikin Altherma air-to-water heat pump systems serving space heating and a domestic hot water cylinder furnace — American Standard gas furnaces whose integrated controls retain a stored fault history alongside the current status boiler — Baxi domestic boilers covered by the manufacturer E133 guidance ductless-mini-split — Blueridge BMKH ductless mini-split systems documented in the Blueridge manual library ductless-mini-split — Aurora Xtreme Inverter 36,000 BTU cooling-only 220 V heat-pump — Aquarea air-to-water heat pumps ductless-mini-split — Samsung indoor air conditioner units that display the C1 group of service codes described in Samsung support material furnace — Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, covered by troubleshooting guide 58-3T ductless-mini-split — Toshiba air conditioning equipment using the fault code tables published in the Toshiba United Kingdom technical handbook ductless-mini-split — Haier residential split air conditioners documented in the Haier service and resource library boiler — Worcester Bosch Greenstar gas boilers using the two-part display and fault code convention described in Worcester service instructions ductless-mini-split — Friedrich Floating Air ductless indoor units documented in the Friedrich product resource library
P8 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mr Slim families covered by Mitsubishi Electric's P8 reference

Mitsubishi Electric P8 fault: what the code actually narrows down

Mitsubishi Electric P8 reports an abnormal piping-temperature relationship. It can follow low refrigerant flow, a restricted circuit, a displaced or faulty thermistor, or crossed piping and wiring on some multi systems; P8 does not identify one failed part. Applies to: Mr Slim families covered by Mitsubishi Electric's P8 reference This interpretation is limited to Mitsubishi Electric systems included in the cited P8 reference. It does not apply to Mitsubishi Heavy Industries equipment, and the exact service sequence must be selected by the complete indoor and outdoor model numbers. Owner-safe checks: Photograph the full code and both model plates, then record the mode and elapsed run time when P8 returns. Qualified technician: Refrigerant measurements, thermistor testing, terminal checks, and correction of paired piping or wiring belong to qualified service personnel.

Refer to qualified technician View Guide →
P6 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mitsubishi Electric Mr Slim and M-Series systems that publish the P-series protection table

Mitsubishi Electric P6 error code: coil freeze or overheat protection

Mitsubishi Electric assigns P6 to a freezing or overheating protection trip at the indoor coil. In cooling the coil pipe temperature fell far enough to risk ice, and in heating it climbed too high, so the control stopped the compressor. It points at airflow across the coil, the coil thermistor, or the refrigerant condition rather than at one named part. Applies to: Mitsubishi Electric Mr Slim and M-Series systems that publish the P-series protection table This reading follows Mitsubishi Electric literature for the Mr Slim and M-Series families that publish a P-series protection table. Other Mitsubishi Electric ranges, and Mitsubishi Heavy Industries equipment, use different code tables, so match the indoor and outdoor model numbers first. Owner-safe checks: With the system off, remove and clean the indoor filters, dry them fully, refit them, and confirm nothing blocks the intake or outlet of the indoor unit. | Note whether P6 happened in cooling or heating, whether the coil was frosted, and whether airflow felt weak beforehand. Qualified technician: Checking refrigerant charge, cleaning the indoor coil or blower wheel, and measuring or replacing the coil thermistor require a qualified technician with gauges.

Refer to qualified technician View Guide →
P5 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mitsubishi Electric indoor units that publish the P-series protection table, including Mr Slim cassette, ducted, and ceiling-suspended indoor units

Mitsubishi P5: the drain protection stopped the unit before water did

P5 is a drain protection stop on a Mitsubishi Electric indoor unit. The control saw the float switch rise, or it saw the drain pump circuit fail to respond, and it shut cooling down to keep the condensate tray from overflowing. The code proves water did not leave the tray fast enough. It does not name the blockage, the pump, or the switch as the failed part. Applies to: Mitsubishi Electric indoor units that publish the P-series protection table, including Mr Slim cassette, ducted, and ceiling-suspended indoor units P5 is read here from the Mitsubishi Electric fault-code reference for the indoor families that publish the P-series table. Wall-mounted units without a condensate pump do not carry the same detection, and a Mitsubishi Electric controller fitted to another manufacturer's indoor unit will not follow this table. Match the code to the indoor unit model on its own rating label rather than to the outdoor unit. Owner-safe checks: Switch the indoor unit to fan only or off so the coil stops producing condensate, and leave it that way until the fault is assessed. | Look at the visible outdoor end of the condensate line during a period when the unit had been cooling, and note whether any water discharged. | Photograph the controller showing P5 together with the indoor unit address, and note the outdoor temperature and humidity at the time. Qualified technician: Checking the float switch, testing the drain pump circuit, and clearing a condensate line inside the indoor unit require the electrical enclosure to be opened, which is qualified service work. | Water staining on a ceiling, a wall, or an electrical accessory near the unit is a stop condition. Isolate the indoor unit and arrange service rather than running it to see whether the code returns.

Refer to qualified technician View Guide →
P2 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mitsubishi Electric indoor units publishing the P-series fault table, including M-Series wall units and Mr Slim indoor equipment

Mitsubishi P2: the pipe sensor that tells defrost and freeze control what to do

P2 identifies an abnormality in the indoor pipe temperature thermistor, the sensor clamped to the indoor heat exchanger rather than the one reading room air. Its value drives freeze protection in cooling and heat-exchanger temperature logic in heating, so the control stops rather than run those functions blind. Applies to: Mitsubishi Electric indoor units publishing the P-series fault table, including M-Series wall units and Mr Slim indoor equipment The entry read here belongs to Mitsubishi Electric indoor units that publish the P-series table. Some Mitsubishi indoor units carry more than one pipe thermistor, and the table then separates them by code, so the position of the failed sensor comes from the service manual for that exact indoor model rather than from the code alone. Owner-safe checks: Switch the affected indoor unit to fan only if the coil has visible frost, and let it thaw without heat, tools, or water. | Note the indoor address, the room, and whether other heads on the same system continue to work normally. | Write down any period in the preceding weeks when heating airflow was slow to start or cooling produced indoor frost. Qualified technician: Verifying sensor mounting, measuring thermistor resistance against the published curve, and inspecting the indoor harness all need the indoor casing opened by a qualified technician. | Repeated indoor coil frosting alongside P2 needs refrigerant and airflow assessment, which is licensed work and not an owner task.

Refer to qualified technician View Guide →
P1 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment

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 has no basis for deciding capacity and stops rather than guessing. Applies to: Mitsubishi Electric indoor units that publish the P-series fault table, covering Mr Slim and M-Series indoor equipment 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 acting on it. Owner-safe checks: 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 controller display, the indoor address, and whether the fault follows any recent maintenance. Qualified technician: 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 it has been inspected.

Refer to qualified technician View Guide →
L9 ProfessionalRequired
Mitsubishi Electric • heat-pump — Ecodan FTC5 cylinder units, EHPT20X-MHCW and EHST20(D)(C)-MHCW

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 reports a measurement, not a failed pump. Applies to: Ecodan FTC5 cylinder units, EHPT20X-MHCW and EHST20(D)(C)-MHCW 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. Owner-safe checks: 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 falling, since a leak is on the manufacturer's cause list. | Record whether the code appears at start-up or during steady running, and whether the circuit has been opened recently. | Check that no radiator valve or zone valve has been closed off since the system last ran normally. Qualified technician: 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 settings on the FTC board are commissioning parameters, and changing one without knowing which circuits exist can hide the fault rather than clear it. | Replacing or resizing the circulation pump is a design decision about system head, not a parts swap.

Refer to qualified technician View Guide →
E6 ProfessionalRequired
Mitsubishi Electric • ductless-mini-split — Mitsubishi Electric M-Series and Mr Slim systems that publish the E-series communication table

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. Applies to: Mitsubishi Electric M-Series and Mr Slim systems that publish the E-series communication table 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
P2 ProfessionalRequired
Midea • heat-pump — Midea residential split air conditioners and heat pumps covered by the Midea online troubleshooting code reference

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 failed. Applies to: Midea residential split air conditioners and heat pumps covered by the Midea online troubleshooting code reference 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. Owner-safe checks: 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 and how the system had been performing in the weeks before. Qualified technician: 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.

Refer to qualified technician View Guide →
E3 ProfessionalRequired
Midea • ductless-mini-split — Midea residential split air conditioners covered by the Midea online troubleshooting code reference

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 caused it. Applies to: Midea residential split air conditioners covered by the Midea online troubleshooting code reference 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. Owner-safe checks: 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, which setting produced it, and approximately what week it began. Qualified technician: 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 assembly can start without warning.

Refer to qualified technician View Guide →
E2 ProfessionalRequired
Midea • ductless-mini-split — Midea wall-split systems, and systems built on the same platform sold under other names, that publish E2

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. Applies to: Midea wall-split systems, and systems built on the same platform sold under other names, that publish E2 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
E1 ProfessionalRequired
Midea • ductless-mini-split — Aurora Xtreme Inverter 36,000 BTU cooling-only 220 V

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. Applies to: Aurora Xtreme Inverter 36,000 BTU cooling-only 220 V 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 page. Owner-safe checks: 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. Qualified technician: Signal-voltage measurement, reactor inspection, and PCB replacement are technician procedures. | Do not open the outdoor electrical compartment or attempt live meter tests.

Refer to qualified technician View Guide →
Mode conflict ProfessionalRequired
LG • 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: 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 what it asked for. Applies to: LG multi-split systems where several indoor units share a single outdoor unit, as described in LG help-library guidance 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. Owner-safe checks: 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 automatic selection. Qualified technician: 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.

Refer to qualified technician View Guide →
CH21 / CH23 / CH26 / CH29 ProfessionalRequired
LG • 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 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 compressor side of the system. Applies to: LG residential air conditioners covered by the United States help-library article grouping these codes as outdoor compressor or circuit board problems 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 rather than from this article. Owner-safe checks: 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, and whether anything else in the property is misbehaving at the same time. Qualified technician: 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.

Refer to qualified technician View Guide →
CH07 ProfessionalRequired
LG • multi-zone — LG multi-split systems where several indoor units share one outdoor unit

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. Applies to: LG multi-split systems where several indoor units share one outdoor unit 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
CH05 ProfessionalRequired
LG • ductless-mini-split — LG single-zone systems in MFL41161610

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. Applies to: LG single-zone systems in MFL41161610 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
CH04 ProfessionalRequired
LG • ductless-mini-split — LG single-zone systems in general service manual MFL41161610

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. Applies to: LG single-zone systems in general service manual MFL41161610 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. Owner-safe checks: 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 electrical cover. Qualified technician: 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.

Refer to qualified technician View Guide →
CH01 / CH02 / CH06 / CH12 ProfessionalRequired
LG • ductless-mini-split — LG residential air conditioners covered by the United States help-library article that groups these codes as sensor problems

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 published customer guidance stops at the category. Applies to: LG residential air conditioners covered by the United States help-library article that groups these codes as sensor problems 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's own manual. Owner-safe checks: 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 and record both figures before the reset. Qualified technician: 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.

Refer to qualified technician View Guide →
Control restart ProfessionalRequired
Lennox • controls-thermostats — Lennox iComfort communicating thermostats and the equipment controls they are paired with

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 alarming and means something specific. Applies to: Lennox iComfort communicating thermostats and the equipment controls they are paired with 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
418 / 419 ProfessionalRequired
Lennox • heat-pump — XP17 heat pumps with iComfort communicating controls

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. Applies to: XP17 heat pumps with iComfort communicating controls 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. Owner-safe checks: 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. Qualified technician: 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.

Refer to qualified technician View Guide →
411 ProfessionalRequired
Lennox • heat-pump — XP17 heat pumps with iComfort communicating controls

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. Applies to: XP17 heat pumps with iComfort communicating controls 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. Owner-safe checks: Save the complete iComfort alert history, operating mode, filter condition, weather, visible outdoor clearance, and recent service without opening equipment. Qualified technician: Pressure-switch, wiring, refrigerant, airflow commissioning, control-log, and live electrical diagnosis require a Lennox-qualified technician.

Refer to qualified technician View Guide →
Previous Page 4 of 9 Next