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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 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 ductless-mini-split — Fujitsu General residential indoor units that report faults through operation and timer indicator lamps 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
2 blinks ProfessionalRequired
Rheem • furnace — Rheem R96V modulating condensing gas furnaces documented in the Rheem service literature

Rheem two blinks: the draft proving circuit stopped the sequence

Two blinks on a Rheem furnace control identifies a pressure switch condition in the draft proving circuit. The switch is the device that tells the control whether the inducer has established the airflow the burner needs, so the blink count locates the circuit that failed to reach its expected state rather than the part that caused it. Applies to: Rheem R96V modulating condensing gas furnaces documented in the Rheem service literature This reading follows the diagnostic table published for the Rheem R96V modulating condensing furnace. Rheem and Ruud have used different blink assignments across control generations, and a chart written for another Rheem furnace line can give a different meaning for the same count. Match the model on the rating plate. Owner-safe checks: Count the blinks carefully, since two blinks and three blinks are easy to confuse when the pause between groups is short. | View the vent and intake terminations from ground level and note ice, snow, nests, or vegetation without climbing or reaching in. | Record the outdoor temperature, wind, and whether ignition was ever attempted on each failed cycle. Qualified technician: Measuring draft pressure against the published value, inspecting the inducer wheel, and clearing condensate paths are licensed gas-furnace tasks. | A pressure switch must never be bridged or bypassed to make a furnace run, because it is the only device confirming that combustion products are leaving the building.

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1 Blink ProfessionalRequired
Rheem • furnace — Rheem residential gas furnaces covered by the published technical FAQ

Rheem furnace one-blink lockout: four trials or four flame failures

Rheem publishes the one-blink code as no flame sensed after four ignition trials, or four flame failures during one call for heat. Those are two different histories: in the first the burner never established a flame, and in the second it lit four times and the signal was lost each time. To clear it, Rheem has the owner interrupt the 115 volt supply, or switch the thermostat off, for a count of five to ten seconds. Applies to: Rheem residential gas furnaces covered by the published technical FAQ This code and reset method come from Rheem's published gas furnace technical FAQ and apply to the Rheem furnaces it covers. Ruud furnaces share much of the Rheem platform but their own literature governs, and a single flash on another manufacturer's control means something else entirely. Owner-safe checks: Stand where you can hear the furnace and note whether the burner is audible on each attempt before the lockout. | Count the blinks and confirm the pattern repeats rather than changing between cycles. | Check that other gas appliances in the house work, without operating a valve or opening the furnace cabinet. | Confirm the filter is clean and every supply register is open, since airflow faults produce a different code. | Clear the lockout once, by interrupting the 115 volt supply or the thermostat for a count of five to ten seconds. Qualified technician: The same lockout returning after one reset with the gas supply confirmed. | A two-blink or four-blink pressure-switch pattern, which is a separate combustion-safety service path. | Any work on the flame sense rod, gas valve, or manifold pressure, all of which need the burner compartment opened. | Suspected supply polarity or grounding problems, which are electrical rather than heating work. | Any smell of gas, which is an evacuation and an emergency call rather than a service request.

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P-series ProfessionalRequired
Pioneer • ductless-mini-split — Pioneer Diamante and Quantum ductless systems whose code lists are published in Pioneer support

Pioneer P codes: protections that stop the system on purpose

A Pioneer code beginning with P marks a protection: the equipment measured something outside its permitted range and shut itself down before harm could follow. That is a description of a decision, not an accusation against a component, and the difference decides where a technician starts. Applies to: Pioneer Diamante and Quantum ductless systems whose code lists are published in Pioneer support Pioneer publishes code lists per system family, and the Diamante and Quantum lists are the ones referenced here. Pioneer equipment from earlier generations, and equipment sold under other names on related hardware, carries its own list. Confirm the family from the indoor and outdoor model numbers first. Owner-safe checks: Photograph the display showing the full code, including every character after the letter. | Clean the indoor filters and clear the space around the outdoor unit, then note whether behaviour changes. | Log the run time before each shutdown and the outdoor temperature at the time. Qualified technician: Weighing the charge, hunting a leak, and washing a coil all fall inside the certification regimes: EPA Section 608 across the United States, and the F-Gas framework in Britain and the European Union. | Repeated restarts return the equipment to the condition the protection stopped, so they are not a substitute for a measurement.

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Fd / Fy / Hd ProfessionalRequired
Pioneer • ductless-mini-split — Diamante and Quantum systems in the manufacturer code list

Pioneer Fd, Fy, and Hd: three codes from the leak detector

Pioneer assigns three different codes to the refrigerant detector. Fd reports a detector fault, Fy reports refrigerant leakage detected, and Hd reports that the leak detector is detecting refrigerant. Only two of the three say anything about refrigerant being present. Applies to: Diamante and Quantum systems in the manufacturer code list These meanings come from the Pioneer code list published for Diamante and Quantum systems. Pioneer maintains separate code documentation for its dehumidifiers, its recreational vehicle systems, and the Vertex ducted central split range, and the same characters on another manufacturer's equipment mean something else entirely. Owner-safe checks: Photograph the exact characters on the display, since Fd, Fy, and Hd are three different messages. | Ventilate the room and stop the system if the code is one of the two that report refrigerant present. | Write down any recent work, decorating, or aerosol use near the indoor unit and the date the code first appeared. Qualified technician: Refrigerant detection, recovery, leak location, and recharging require a certified technician with the correct equipment for the refrigerant in the system. | A faulty detector reported by Fd should be repaired rather than bypassed, because the system is running without the monitoring it was built with.

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E1 / EL01 / EL 01 ProfessionalRequired
Pioneer • ductless-mini-split — Discontinued Quantum WYS, CYB, RYB, UYB, and FYB

Pioneer E1, EL01, or EL 01: Quantum communication error

For the discontinued Pioneer Quantum families and models listed in the official guide, E1, EL01, or EL 01 means the indoor and outdoor units cannot communicate successfully. Applies to: Discontinued Quantum WYS, CYB, RYB, UYB, and FYB This is the older of two Pioneer E1 meanings. It applies to the discontinued Quantum WYS, CYB, RYB, UYB, and FYB families and the companion models the official guide lists. On the current Pioneer families, E1 reports a room temperature sensor failure instead, which is a different fault with a different diagnosis. Owner-safe checks: Confirm the unit is one of the exact discontinued Quantum families covered by the guide. | Record whether the code appeared after installation, service, or a power interruption. Qualified technician: The official diagnostic path includes terminal, voltage, PCB, and high-voltage component tests that require qualified service. | Do not use this page for newer Pioneer families where E1 can mean a sensor fault.

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E1 ProfessionalRequired
Pioneer • ductless-mini-split — Diamante Essenza, Diamante Pro, Quantum Fresh, Hyperformance, and Ultra

Pioneer E1 error code: room-temperature sensor failure

On the Pioneer families listed by the current official guide, E1 indicates an indoor room-temperature sensor failure; this differs from the communication meaning used by specified discontinued Quantum equipment. Applies to: Diamante Essenza, Diamante Pro, Quantum Fresh, Hyperformance, and Ultra The sensor meaning applies to the models the current Pioneer guide lists, including the WYT, CYT, RYT, and UYT designations shown above. If your indoor unit belongs to one of the discontinued Quantum families, the same characters report a communication failure and the diagnosis is completely different. Owner-safe checks: Compare both indoor and outdoor model numbers with the guide's supported-model list before interpreting E1. | Record the room conditions and whether the displayed temperature appears implausible. Qualified technician: Sensor resistance, connector, and PCB diagnosis requires the exact service data and qualified equipment access. | Do not substitute the older Quantum communication procedure for these listed models.

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H62 ProfessionalRequired
Panasonic • heat-pump — Aquarea air-to-water heat pumps

Panasonic Aquarea H62: read it as a water-flow fault

Panasonic's Aquarea end-user guidance identifies H62 as a water-flow error and directs the owner to an authorised installer. The code says required circulation was not confirmed; it does not decide whether the cause is system pressure, a closed valve, trapped air, blockage, pump operation, sensing, or wiring. Applies to: Aquarea air-to-water heat pumps This answer applies to Panasonic Aquarea air-to-water heat pumps within the cited European end-user manual. Panasonic residential air conditioners use H codes too, but their meanings must not be transferred to Aquarea. Owner-safe checks: Photograph H62 and the visible pressure value, note the active heating or hot-water demand, and check only for external water leakage. Qualified technician: Pump, flow-sensor, valve, strainer, pressure, venting, wiring, and internal hydraulic checks belong to the authorised Aquarea installer.

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H11 ProfessionalRequired
Panasonic • ductless-mini-split — Panasonic wall-mounted split systems that report H-series and F-series self-diagnosis codes

Panasonic H11 error code: no communication between indoor and outdoor

Panasonic assigns H11 to an abnormal serial communication between the indoor and outdoor units. The signal that normally passes over the connecting cable has stopped, so the indoor board cannot exchange data with the outdoor board. It points at the interconnecting wiring or a board circuit at one end. Applies to: Panasonic wall-mounted split systems that report H-series and F-series self-diagnosis codes This reading follows Panasonic self-diagnosis literature for wall-mounted split systems that use the H and F code families. Panasonic Aquarea heat pumps and ducted ranges use different tables, so confirm the indoor and outdoor model numbers first. Owner-safe checks: Run the remote self-diagnosis to confirm the stored code is H11 rather than another H or F code. | With the system off at the isolator, check the visible connecting cable for obvious damage and note whether the outdoor fan turns while H11 is shown. Qualified technician: Checking the connecting cable at the terminals and testing the board communication circuits require isolating power and belong with a Panasonic dealer or qualified technician.

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F11 ProfessionalRequired
Panasonic • ductless-mini-split — Panasonic reverse-cycle wall split systems that report F11 in the self-diagnosis table

Panasonic F11 error code: four-way valve switching fault

Panasonic assigns F11 to a four-way valve switching abnormality. The system commanded the reversing valve to change between heating and cooling, then read the coil temperatures and did not see the change it expected, so it stopped. It points at the valve, its coil, the wiring, or the sensors used to confirm the switch. Applies to: Panasonic reverse-cycle wall split systems that report F11 in the self-diagnosis table This meaning follows Panasonic self-diagnosis literature for reverse-cycle wall split systems that list F11. Cooling-only models do not have a four-way valve, and other Panasonic ranges use different code tables, so confirm the model is a heat pump and check both model numbers. Owner-safe checks: Note which mode the unit was in or changing to when F11 appeared, and whether it had just come out of a defrost cycle. | Note whether the air was the wrong temperature for the selected mode before the unit stopped. Qualified technician: Testing the reversing valve solenoid, inspecting the valve, and reading pressures across it require a technician with gauges, and replacing the valve is sealed-circuit work.

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F-series ProfessionalRequired
Panasonic • ductless-mini-split — Panasonic room air conditioners with the self-diagnosis function described in Panasonic service documentation

Panasonic F-series codes: the self-diagnosis that points at the cycle

Panasonic groups its self-diagnosis codes by leading character, and the F-series concerns the refrigeration cycle rather than communication or sensing alone. An F entry says the equipment evaluated how the cycle was behaving and found it outside what it expects, which is a statement about refrigerant, flow, and heat transfer together. Applies to: Panasonic room air conditioners with the self-diagnosis function described in Panasonic service documentation Panasonic self-diagnosis is present across room air conditioner ranges but the retrieval method and the code tables differ by generation. The codes described here belong to the residential air conditioning documentation; Aquarea air-to-water equipment uses a separate scheme entirely. Owner-safe checks: Find and follow the self-diagnosis retrieval sequence for your model rather than interpreting an indicator pattern by eye. | Clean the indoor filters and confirm the outdoor unit has clear space around it on all sides. | Note how performance changed over recent weeks and time the interval between stop and restart if the system is cycling. Qualified technician: Connecting gauges, measuring charge, and testing expansion device operation are certified refrigerant tasks and require the system to be running under supervision. | Do not add refrigerant in response to a cycle code. Charge is a measured quantity on this equipment, not something to be topped up until symptoms change.

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Alarm log ProfessionalRequired
NIBE • heat-pump — NIBE air source and ground source heat pumps with controllers that store an alarm log and operating history

NIBE alarms: the log is worth more than the alarm on screen

A NIBE controller stores more than the alarm currently displayed. It keeps a history of previous alarms with timestamps and, on many models, operating values recorded alongside them, and that history answers questions the current alarm cannot: whether this has happened before, how often, and under what conditions. Applies to: NIBE air source and ground source heat pumps with controllers that store an alarm log and operating history NIBE controllers differ between the F, S, SMO, and VVM families in what they log and how it is reached, and an alarm number is interpreted against the manual for that controller. A number from one family should not be applied to another even within the NIBE range. Owner-safe checks: Photograph the current alarm, then open the alarm log and photograph the history with its timestamps. | Capture any operating values the controller displays alongside the log, including flow and return temperatures. | Note the outdoor conditions and what the system was being asked for when the alarm occurred. Qualified technician: Refrigerant-side alarms require a certified handler under F-Gas rules in the United Kingdom and European Union and under EPA Section 608 in the United States. | Adjusting flow rates, pump settings, or controller parameters on a heat pump installation affects how the equipment operates across its whole envelope and belongs to the commissioning installer.

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228 ProfessionalRequired
NIBE • heat-pump — F2120 air-to-water heat pumps

NIBE F2120 alarm 228 after unsuccessful defrosting

NIBE's F2120 installer manual associates alarm 228 with ten unsuccessful defrosting attempts. The alarm reports failed recovery across repeated cycles, not a single defective defrost part. Outdoor airflow, ice and drainage, sensors, fan, refrigerant operation, reversing process, and controls need installer evidence. Applies to: F2120 air-to-water heat pumps This definition is for the NIBE F2120 manual cited here. S2125, F2040, exhaust-air, and ground-source NIBE products have different alarm logic even when connected to a similar indoor controller or myUplink. Owner-safe checks: Record alarm history, weather, visible frost, all outdoor clearances, base drainage, runoff, and whether backup heat maintains the building. Qualified technician: Defrost history, sensor, fan, refrigeration, reversing, drainage design, installer-menu, and live electrical checks require a NIBE installer.

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P4 / PC04 ProfessionalRequired
MRCOOL • ductless-mini-split — MRCOOL DIY mini-split generations that report an inverter compressor drive fault

MRCOOL P4 and PC-04 error code: inverter compressor drive fault

MRCOOL uses this code for an inverter compressor drive fault, shown as P4 on generations before the fourth and as PC-04 on fourth generation DIY equipment. The drive electronics that run the compressor have reported an abnormal condition and stopped it. The cause differs between a newly installed system and one that has been running. Applies to: MRCOOL DIY mini-split generations that report an inverter compressor drive fault This meaning follows MRCOOL DIY support literature for the generations that display P4 or PC-04. The generation matters more than the digits, because MRCOOL renumbers codes between series, so identify the DIY generation from the model number before using this page. Owner-safe checks: Identify the DIY generation from the model number so the correct code table and parts list are used. | Isolate power at the breaker for fifteen minutes, then restart once, and note whether P4 or PC-04 returns. Qualified technician: Testing the run capacitor, contactor, inverter module, and compressor current, and checking supply voltage under load, require a qualified technician working at energised terminals.

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P1 / PC-01 ProfessionalRequired
MRCOOL • ductless-mini-split — MRCOOL single-zone and multi-zone families in official support

MRCOOL P1 or PC-01 error code: voltage protection

MRCOOL describes P1 or PC-01 as a voltage-related protection condition; exact terminal layout and acceptable supply depend on whether the documented system is 115 V, 230 V, single-zone, or multi-zone. Applies to: MRCOOL single-zone and multi-zone families in official support What counts as an acceptable supply is not one number across the MRCOOL range. A 115 V single-zone system, a 230 V single-zone system, and a multi-zone system have different expectations and different terminal arrangements, so the official material for your configuration governs, not a figure quoted for a different one. Owner-safe checks: Record the full indoor and outdoor model numbers, displayed code, and whether other circuits in the home lost power. | Check only the normal breaker position and do not repeatedly reset a breaker that trips. Qualified technician: MRCOOL's voltage measurements require panel access and live electrical testing; use a qualified HVAC or electrical professional. | A tripping breaker, heat, odor, or damaged wiring requires the equipment to remain off.

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P0 / PC00 ProfessionalRequired
MRCOOL • ductless-mini-split — MRCOOL mini-splits covered by official P0/PC00 support

MRCOOL P0 or PC00 error code: inverter module protection

MRCOOL identifies P0 or PC00 as an inverter-module or compressor-protection condition associated with abnormal voltage or current, wiring, the inverter module, or the compressor. Applies to: MRCOOL mini-splits covered by official P0/PC00 support P0 and PC00 are the same protection shown by different display generations, in the same way MRCOOL communication faults appear as EL01 or E1. Confirm the characters and the model against the official code table, and do not carry a P code from another brand into MRCOOL equipment, because the letter and number pairings are not an industry standard. Owner-safe checks: Turn the unit off and check for visible outdoor airflow blockage without removing covers. | Record when the code appears and whether it followed an outage or severe weather. Qualified technician: Live supply checks, inverter-module tests, compressor tests, and internal wiring inspection require qualified service. | Do not handle capacitors, DC bus components, or compressor terminals.

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Generation-dependent codes ProfessionalRequired
MRCOOL • ductless-mini-split — MRCOOL DIY ductless systems across the third, fourth, and fifth generations documented in MRCOOL support

MRCOOL DIY codes changed between generations, and so did the format

MRCOOL changed both the numbering and the format of its DIY codes between generations. A condition shown as P4 on earlier equipment appears as PC-04 on fourth generation units, and searching one format while owning the other returns answers that look right and are not. Applies to: MRCOOL DIY ductless systems across the third, fourth, and fifth generations documented in MRCOOL support MRCOOL DIY generations differ in refrigerant, cable, port count, and control firmware as well as in code format. The generation has to be established from the model and the documentation supplied with the equipment, and MRCOOL publishes the differences between fourth and fifth generation explicitly. Owner-safe checks: Photograph the displayed code exactly as it appears, including any hyphen or leading characters. | Find the documentation supplied with the equipment and confirm which DIY generation it covers. | Where more than one MRCOOL system is installed, record which unit each code came from. Qualified technician: Refrigerant work on any generation requires certification, and the newer refrigerant carries its own handling and room-size considerations. | Self-installed equipment does not change who may open a refrigerant circuit. The pre-charged line set is designed to be connected without opening the circuit, and anything beyond that is certified work.

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EL01 / E1 ProfessionalRequired
MRCOOL • ductless-mini-split — MRCOOL generations and models identified in official support

MRCOOL EL01 or E1 error code: communication malfunction

MRCOOL identifies EL01 or E1 on the supported mini-split families as an indoor-to-outdoor communication malfunction, which implicates the connection path without proving one component failed. Applies to: MRCOOL generations and models identified in official support MRCOOL revises its code display between product generations, which is why the same fault reaches you as EL01 on some equipment and E1 on others. Match the characters you see and the generation of your indoor unit against the official code table before acting, because the table is the thing that resolves which entry applies. Owner-safe checks: Match the displayed code and model generation to MRCOOL's official code table. | With power off at the breaker, wait as the official guide directs and note whether one restart clears the display. Qualified technician: Terminal access, voltage measurements, board LEDs, and component isolation expose hazardous electrical parts and are technician work. | If the code returns, contact qualified service or MRCOOL support with model and serial information.

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E-series ProfessionalRequired
Mitsubishi Heavy Industries • ductless-mini-split — Mitsubishi Heavy Industries room air conditioners documented in the MHI user manual library

Mitsubishi Heavy Industries E codes are not Mitsubishi Electric codes

Mitsubishi Heavy Industries publishes its own E-series fault codes, and they are unrelated to the codes used by Mitsubishi Electric despite the shared name. The two are separate companies with separate engineering, so a code table found for one will mislead on the other, sometimes convincingly. Applies to: Mitsubishi Heavy Industries room air conditioners documented in the MHI user manual library This page concerns Mitsubishi Heavy Industries room air conditioners documented in the MHI user manual library. Mitsubishi Electric equipment, sold as M-Series, Mr Slim, and Ecodan, is documented separately and carries different code meanings for the same characters. Owner-safe checks: Read the full manufacturer name and model number from the outdoor unit data plate and write them down before searching anything. | Note which indoor units are affected and which continue to work normally. | Confirm whether the remote control is still being acknowledged by the affected unit. Qualified technician: Testing the interconnecting cable, inspecting boards, and correcting address or configuration settings require the casings to be opened by a qualified technician. | Interconnecting cable between indoor and outdoor units carries mains voltage on this equipment, so it is not something to inspect, strip, or reterminate without the appropriate qualification.

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U6 ProfessionalRequired
Mitsubishi Electric • heat-pump — Mitsubishi Electric inverter outdoor units publishing the U-series fault table, including M-Series single-zone and MXZ multi-zone equipment

Mitsubishi U6: the inverter cut the compressor current before anything melted

U6 is raised when the outdoor inverter detects compressor current or power module conditions outside the range it will drive. It is an electrical protection acting in milliseconds, which is why the code arrives as an abrupt stop rather than a gradual loss of output. The detection names the current, not the cause of the current. Applies to: Mitsubishi Electric inverter outdoor units publishing the U-series fault table, including M-Series single-zone and MXZ multi-zone equipment The entry described here belongs to Mitsubishi Electric outdoor units publishing the U-series table. Multi-zone outdoor units serving several indoor heads report the code centrally, so the address shown does not identify a room. Confirm the outdoor model from its plate before applying this reading. Owner-safe checks: Attempt at most one restart from the controller, then stop and note how long the outdoor unit ran before the code returned. | Check whether other appliances on the property are behaving normally and whether any protective device in the consumer unit or panel has operated. | Leave the isolator on and the operation off for several hours before any further attempt if the system has been unused for a long period. Qualified technician: Measuring compressor winding resistance, drive output, and supply voltage under load requires opening an energised outdoor enclosure and is qualified work. | A burning smell, visible scorching, or a protective device that trips when the unit starts is a stop condition. Isolate at the dedicated switch and arrange service without further attempts.

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U2 ProfessionalRequired
Mitsubishi Electric • heat-pump — Mitsubishi Electric outdoor units publishing the U-series fault table, including M-Series and MXZ multi-zone outdoor equipment

Mitsubishi U2: high discharge temperature is a charge question, not a compressor verdict

U2 is an outdoor protection stop raised when the compressor discharge temperature rises beyond the limit the control allows, a condition the reference also ties to refrigerant shortage. High discharge temperature is what a compressor does when it has too little refrigerant returning to cool it, so the code is a symptom of the refrigerant circuit rather than proof the compressor is damaged. Applies to: Mitsubishi Electric outdoor units publishing the U-series fault table, including M-Series and MXZ multi-zone outdoor equipment This applies to Mitsubishi Electric outdoor units that publish the U-series table. The same two characters appear on other manufacturers with unrelated meanings, and Mitsubishi Heavy Industries is a separate company with its own code set. Take the reading from the outdoor unit model plate, not from the brand name on the indoor grille. Owner-safe checks: Turn the system off at the controller and leave it off, since repeated restarts run the compressor under the condition that triggered the limit. | Walk the visible line set and the outdoor unit looking for oil film, frost patches, or a disturbed insulation run, and photograph anything you find. | Write down how the system had been performing over the preceding weeks and the outdoor conditions when it stopped. Qualified technician: Measuring charge, searching for a leak, recovering refrigerant, and testing the discharge thermistor are certified refrigerant-handling activities under EPA Section 608 in the United States and F-Gas rules in the United Kingdom and Europe. | Do not add refrigerant, tighten a flare, or operate the system to see whether the code stays away. Running a compressor at high discharge temperature is what the protection exists to prevent.

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