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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 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
Room demand not met ProfessionalRequired
Drayton • controls-thermostats — Drayton Wiser multi-zone heating systems using a heat hub with room thermostats and smart radiator thermostats

Drayton Wiser: one cold room when the rest of the house is warm

A Wiser system asks the boiler for heat only when at least one room wants it, and then opens that room's radiator valves. A single cold room therefore means either that room is not asking, or it is asking and its valve is not opening, and those are separate faults with separate fixes. Applies to: Drayton Wiser multi-zone heating systems using a heat hub with room thermostats and smart radiator thermostats Wiser covers single-zone and multi-zone arrangements with different combinations of hub, room thermostats, and radiator thermostats, and behaviour depends on how the system was configured rather than only on what is installed. The Drayton Wiser documentation for your arrangement is the reference. Owner-safe checks: Confirm whether the rest of the house heats normally during the same period, which separates a room fault from a system fault. | Check and replace the batteries in the affected radiator thermostat, since a device without power cannot move a valve. | Listen at the radiator when a demand is set, since a valve that is being driven makes an audible movement. Qualified technician: A radiator that stays cold with its valve confirmed open, or that is cold at the bottom while hot at the top, is a hydraulic matter for a heating engineer. | Removing a radiator thermostat from a valve body, or changing a valve, risks releasing water from a sealed system and sits outside owner maintenance.

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Series-dependent codes ProfessionalRequired
Della • ductless-mini-split — Della ductless mini-split systems documented in the Della manual and support library

Della codes: a value brand still needs the right document

Della supports its equipment through documentation tied to each product line rather than through a single brand-wide code list. An owner therefore needs the model number before the code means anything, and that is the step most likely to be skipped on lower-cost equipment where the manual has been discarded. Applies to: Della ductless mini-split systems documented in the Della manual and support library Della equipment is manufactured to order and its documentation is organised per model. A code list found under the brand name alone may describe a different product line, and the manual or support document that matches the model number on the data plate is the only reliable mapping. Owner-safe checks: Photograph both data plates and record the complete model numbers before contacting anybody. | Photograph the displayed code before power is interrupted for any reason. | Note whether the system fails at startup or after a period of operation, and how long it ran. Qualified technician: The conductors linking the wall unit to the condenser sit at mains potential, which puts any probing, stripping, or reterminating of them outside owner work. | Conditions reached after a period of operation involve the sealed refrigerant circuit, which requires certification to open regardless of what the equipment cost.

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E5/5E ProfessionalRequired
Della • ductless-mini-split — Econo, Vario, Optima, Motto, and Umbra mini-splits

Della E5 error code: the series changes the meaning

Della does not assign one universal meaning to E5. Its published table gives E5 as an indoor/outdoor mismatch on Econo, Vario, and Optima systems, but E5 or 5E as indoor/outdoor communication failure on Motto and Umbra systems. Read the model family before the code. Applies to: Econo, Vario, Optima, Motto, and Umbra mini-splits The distinctions here follow Della's own series table. They do not cover every Della generation, and a retail listing name is not a substitute for the model label when choosing the correct manual. Owner-safe checks: Photograph both model labels and the exact E5 or 5E orientation, then record whether the fault existed from initial commissioning. Qualified technician: Equipment matching, configuration, field wiring, voltage, communication, and board diagnosis belong to the installer or Della-authorised service.

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E3 / E7 / E8 / EH / Ej / En / Ey ProfessionalRequired
Della • ductless-mini-split — Econo IF, Vario TL, and Optima TP single zone, and the multi-zone systems sharing the table

Della outdoor sensor codes: the letter after E names the sensor

All seven codes report a failed outdoor temperature sensor, and the character after the E identifies which one. None of them is a compressor fault, a refrigerant fault, or an indoor fault. Applies to: Econo IF, Vario TL, and Optima TP single zone, and the multi-zone systems sharing the table This table is published for the Della Econo IF, Vario TL, and Optima TP single zone series, and the multi-zone systems that share it. The Motto JA and Umbra JPB series use a different set entirely, where outdoor sensor faults appear as F codes, so the series has to be established before any of this applies. Owner-safe checks: Photograph the display so the exact character after the E is preserved, since several of them are easy to misread. | Note whether the code is constant or intermittent, and what the weather was doing when it appeared. | Record any work carried out at the outdoor unit since the system last ran normally. Qualified technician: Sensor circuits, connectors, and their resistance measurements sit inside the outdoor electrical compartment and are technician work with the supply isolated. | Question any proposal to replace a compressor or a control board on the strength of a code from this sensor table.

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Hot water duty conditions ProfessionalRequired
Daikin Altherma • heat-pump — Daikin Altherma air-to-water heat pump systems serving space heating and a domestic hot water cylinder

Daikin Altherma hot water faults: two duties competing for one machine

An Altherma serves space heating and the hot water cylinder from one heat pump, and it cannot do both at once. Priority settings decide which duty wins, so heating that pauses during a cylinder reheat, or hot water that takes longer than a boiler did, is the system working as designed rather than reporting a fault. Applies to: Daikin Altherma air-to-water heat pump systems serving space heating and a domestic hot water cylinder Altherma covers split, monobloc, and integrated cylinder configurations across several generations, with different controllers and different parameter names. The installation and operation manual for your configuration governs, and hot water behaviour in particular depends on commissioning choices as much as on the hardware. Owner-safe checks: Note whether space heating pauses coincide with hot water production, which distinguishes priority switching from a fault. | Time a full cylinder reheat and record the cylinder temperature setting alongside it. | Check whether a disinfection cycle is scheduled and at what time, since that is when the element is expected to run. Qualified technician: Cylinder temperature settings, priority parameters, and disinfection schedules affect both safety and running cost, and the installer who commissioned the system should change them. | Anything on the sealed refrigerant side of an Altherma needs a certified handler, regardless of whether the symptom appears on the hot water side.

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7H ProfessionalRequired
Daikin Altherma • heat-pump — Altherma 3 R MT with ELBH-E or ELBX-E and ERRA08-12

Daikin Altherma 7H subcodes: identify the failed flow check

On the documented Daikin Altherma 3 R MT, 7H is incomplete without its suffix. 7H-01 is a general water-flow problem; 7H-04 relates to domestic hot water, 7H-05 to heating or sampling, 7H-06 to cooling or defrost, 7H-07 to pump deblocking, and 7H-08 to pump feedback. Applies to: Altherma 3 R MT with ELBH-E or ELBX-E and ERRA08-12 These subcodes belong to the ELBH-E and ELBX-E indoor units paired with ERRA08-12 equipment in the cited European installer reference. Other Altherma generations and monoblocs use different tables. Owner-safe checks: Capture the complete 7H suffix, both model labels, active mode, visible pressure, outdoor weather, pump sound, open zones, and recent hydraulic work. Qualified technician: Flow measurement, valves, filters, pumps, feedback, sensing, venting, configuration, electrical, and refrigerant work require an Altherma-qualified installer.

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UF ProfessionalRequired
Daikin • ductless-mini-split — Daikin multi-split systems and splits that publish UF for a wiring and piping combination fault

Daikin UF error code: piping and wiring do not match

Daikin assigns UF to a mismatch between the control wiring and the refrigerant piping. On a multi-split the cable from an indoor head lands on one outdoor port while its pipes connect to a different port, so the system cannot pair a head with its circuit. It also covers wrong field wiring and a shortage detected during the check. Applies to: Daikin multi-split systems and splits that publish UF for a wiring and piping combination fault This meaning follows Daikin literature for multi-split and split systems that list UF as a field wiring and piping combination fault. Other Daikin ranges use different U-series codes, so confirm the outdoor unit and every connected indoor model before acting. Owner-safe checks: Note whether UF appeared at first commissioning or right after an indoor head was added, moved, or rewired, and which zones do not respond. | Keep a list of which room each indoor unit serves so the installer can match heads to outdoor ports quickly. Qualified technician: Tracing cables and pipes to outdoor ports and correcting the connections means opening the outdoor electrical cover and working at the terminals, which is installer work.

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UA ProfessionalRequired
Daikin • ductless-mini-split — Daikin split and multi-split systems that publish UA for an indoor and outdoor combination fault

Daikin UA error code: indoor and outdoor unit combination fault

Daikin assigns UA to an improper combination of indoor and outdoor units. The paired models are not compatible, the number of connected indoor units is outside the outdoor unit's limit, the refrigerant types do not match, or a replacement control board was fitted without its combination setting being made. Applies to: Daikin split and multi-split systems that publish UA for an indoor and outdoor combination fault This meaning follows the Daikin malfunction code table for split and multi-split systems that list UA. SkyAir and VRV ranges assign UA-adjacent codes differently, so confirm the outdoor model and every connected indoor model before acting. Owner-safe checks: Note whether UA appeared at first commissioning, after equipment was combined from different kits, or right after a control board was replaced. | Write down the outdoor model and every indoor model with the room it serves, so the installer can check the combination against Daikin's data. Qualified technician: Changing paired equipment, removing indoor units from a multi-split, and making a replacement board's combination setting are all installer or technician tasks.

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U4 ProfessionalRequired
Daikin • light-commercial — SkyAir RZR-P and RZQ-P(9)

Daikin U4 error code: indoor-outdoor transmission error

For the documented Daikin SkyAir RZR-P and RZQ-P(9) systems, U4 is a transmission error between indoor and outdoor units after normal communication is absent for the specified interval. Applies to: SkyAir RZR-P and RZQ-P(9) This definition is taken from the SkyAir service manual covering RZR-P and RZQ-P(9) equipment and the indoor units listed with it. Daikin uses structured code letters across product lines that share little else, so a U4 on VRV, Altherma, or a residential split needs the manual for that line rather than this page. Owner-safe checks: Write down the full controller code and every connected indoor and outdoor model number. | Check only normal user-accessible power controls and note whether other units on the same system operate. Qualified technician: Transmission wiring, fuses, fan motors, and PCBs require qualified electrical diagnosis. | Multi-unit SkyAir systems should be diagnosed as a network rather than by replacing the first board named.

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U2 ProfessionalRequired
Daikin • 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

Daikin U2: power supply malfunction or an instantaneous power failure

In the Daikin malfunction chart, U2 belongs to the system division and reads as a malfunction of the power supply or an instantaneous power failure. That covers both a supply that briefly disappeared and a supply that is present but outside what the drive will work with, which is why one U2 after a storm and a U2 that repeats every day mean unrelated things. Applies to: Daikin equipment covered by the SM-TS3 malfunction chart, where the U division reports system-level conditions across room air, SkyAir, and VRV The reading is taken from the Daikin After Sales Service chart, where the U division covers system conditions rather than one unit. Some Daikin equipment, including the room air lines, presents a related shortage entry as U0, so confirm which digit is displayed before treating the fault as electrical. Owner-safe checks: Check whether a power cut, a storm, or electrical work coincided with the code, and write down what you find. | Confirm that the dedicated isolator and any protective device serving the equipment are in their normal operating position. | Read the supply voltage and frequency printed on the outdoor unit data plate so the figures are available to service. Qualified technician: Measuring supply voltage under load, inspecting isolator and terminal connections, and testing the drive input are qualified electrical tasks. | A protective device that operates repeatedly, a burning smell, or heat at an isolator is a stop condition. Leave the supply off and arrange an electrical inspection.

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U0 ProfessionalRequired
Daikin • ductless-mini-split — Daikin room air conditioner splits and multi-split systems that publish U0 in the malfunction code table

Daikin U0 error code: refrigerant shortage on a mini-split

Daikin assigns U0 to a refrigerant shortage. The control has seen the circuit behaving as though there is too little refrigerant, from readings such as a low suction temperature or an abnormal discharge condition. A closed service valve, an undercharge left after install, or a leak all present as U0. Applies to: Daikin room air conditioner splits and multi-split systems that publish U0 in the malfunction code table This meaning follows the Daikin malfunction code table for room air conditioner and multi-split systems that list U0. SkyAir, VRV, and Altherma ranges use their own code sets, so confirm the indoor and outdoor model numbers before applying this page. Owner-safe checks: Note whether the system is newly installed or has a long service history, and whether output faded gradually or stopped suddenly before U0. | Check from the ground for oily residue at pipe joints or unusual frosting on the outdoor unit, without touching the pipework or valves. Qualified technician: Refrigerant-circuit diagnosis and charging require a qualified technician with the applicable refrigerant handling credential.

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F3 ProfessionalRequired
Daikin • heat-pump — Daikin outdoor equipment covered by the SM-TS3 malfunction chart, spanning room air, SkyAir, and VRV outdoor units

Daikin F3: discharge pipe temperature outside what the circuit allows

Daikin's malfunction chart lists F3 against discharge pipe temperature. The thermistor on the compressor discharge line has reported a temperature the control will not run at, and because refrigerant flow is what keeps that line cool, the reading is a statement about the circuit rather than about the pipe. Applies to: Daikin outdoor equipment covered by the SM-TS3 malfunction chart, spanning room air, SkyAir, and VRV outdoor units Taken from the Daikin After Sales Service malfunction chart, where the F division belongs to the outdoor unit and the detail code selects the subsystem. Sensor positions and the thresholds behind them come from the service manual for the specific outdoor model, so a code alone does not give you a temperature to compare against. Owner-safe checks: Stop calling for heating or cooling and leave the system off, since each further cycle runs the compressor toward the same limit. | Walk the visible line set and outdoor unit looking for oil film or localised frost, and photograph anything unusual without touching it. | Record how long the outdoor unit runs before it stops, and how performance had changed over the preceding weeks. Qualified technician: Charge measurement, leak detection, recovery, and discharge thermistor testing are certified refrigerant activities under EPA Section 608 and under F-Gas rules in the United Kingdom and European Union. | Adding refrigerant without finding the loss, or restarting to see whether the code stays away, both put the compressor back into the condition the protection stopped.

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E7 ProfessionalRequired
Daikin • heat-pump — Daikin outdoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV outdoor equipment

Daikin E7: the outdoor fan motor system stopped reporting what it should

Daikin places E7 in the outdoor unit division as a malfunction of the outdoor fan motor system. The word system is doing real work in that phrase: the entry covers the motor, the drive circuit that powers it, and the feedback path that confirms it turned. Seeing the fan stationary confirms the symptom but not the cause. Applies to: Daikin outdoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV outdoor equipment This meaning is taken from the Daikin malfunction code chart, which assigns codes by division rather than by model. Outdoor fan arrangements differ between a single-fan room air unit and a twin-fan SkyAir or VRV frame, and the checks for each come from the service manual covering that outdoor model. Owner-safe checks: Stop the system from the controller so it is not making repeated start attempts against a fan that is not turning. | Look at the outdoor unit from a safe distance and note whether the blade is completely static, turning slowly, or turning normally. | Isolate the outdoor unit at its dedicated switch before removing leaves or debris resting against the outside of the guard. Qualified technician: Testing the fan drive output, measuring motor windings, and inspecting feedback wiring inside an outdoor enclosure are energised tasks for a qualified technician. | Never reach through or remove the fan guard. A variable-speed outdoor fan can start without notice, including while the system appears to be idle.

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C9 ProfessionalRequired
Daikin • ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems

Daikin C9: the suction air thermistor the room setting depends on

Daikin places C9 in the sensor division against the suction air thermistor, and describes the fault as an abnormal resistance, which covers a disconnection and a short circuit. That sensor reads the air entering the indoor unit, so it is the value the system treats as room temperature and the basis of every capacity decision it makes. Applies to: Daikin indoor units covered by the SM-TS3 malfunction chart, where the C division covers sensor systems The C division on the Daikin chart groups sensor systems, and the detail code selects which sensor. Where a sensor sits inside a particular indoor unit, and what resistance curve it follows, comes from the service manual for that model. A code alone does not tell a technician which physical part to reach for. Owner-safe checks: Note the unit number shown beside C9 and which room it serves before any power is interrupted. | Compare the temperature the controller displays, if it is still visible, against a separate thermometer near the intake. | Confirm filters and panels are correctly seated, and note whether the fault followed any recent cleaning or service. Qualified technician: Measuring thermistor resistance against the published curve and inspecting the indoor board connectors require the casing to be opened by a qualified technician. | A code accompanied by a burning smell, discoloration, or a protective device operating is a stop condition rather than a sensor question.

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A6 ProfessionalRequired
Daikin • ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV indoor equipment

Daikin A6: indoor fan motor locked, overloaded, or badly connected

Daikin lists A6 in the indoor unit division as a fan motor malfunction, described as the motor being locked, overloaded, or suffering from a faulty connection. All three are ways of saying the board commanded a fan speed and did not get the feedback it expected, so the code is about the command-and-feedback loop rather than about a burnt-out motor. Applies to: Daikin indoor units covered by the SM-TS3 malfunction chart, including room air, SkyAir, and VRV indoor equipment The definition here comes from the Daikin malfunction code chart, which is organised by division and detail code rather than by model. Indoor fan arrangements differ sharply between a wall unit, a cassette, and a ducted unit, so the mechanical cause behind the same code is model-specific and is read from that unit's service manual. Owner-safe checks: Switch the affected indoor unit off and leave it off, since running the outdoor unit against a stalled indoor coil is what the protection prevents. | Confirm the filters, front panel, and any decoration panel are correctly seated and latched after recent cleaning. | Write down any noise heard before the fault, the fan speed it occurred at, and roughly when it started. Qualified technician: Reaching into the fan housing, freeing a wheel, and testing motor feedback or winding condition require the indoor casing to be opened by a qualified technician. | Do not attempt to turn the fan wheel by hand through a grille or outlet. The blade edges and the drive arrangement are not designed for that access.

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A5 ProfessionalRequired
Daikin • ductless-mini-split — Daikin 15 and 19 Series

Daikin A5 error code: freeze-up or peak-cut

On Daikin 15 and 19 Series equipment, A5 represents freeze-up protection in cooling or heating peak-cut control when the indoor heat-exchanger temperature crosses the documented limits. Applies to: Daikin 15 and 19 Series The two meanings described here come from the Daikin service manual covering the 15 and 19 Series. Which protection you are looking at depends on the mode the system was running, and other Daikin ranges assign A5 within their own code structure, so start from the manual that matches your model plate. Owner-safe checks: Turn the unit off and inspect the user-removable filter for loading; clean it exactly as the model manual directs. | Confirm furniture, curtains, or closed louvers are not blocking the indoor intake or outlet. Qualified technician: Persistent icing, thermistor testing, coil cleaning beyond routine maintenance, and PCB diagnosis need qualified service. | Do not chip ice from a coil or use heat sources to force thawing.

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A3 ProfessionalRequired
Daikin • ductless-mini-split — Daikin indoor units covered by the SM-TS3 malfunction code chart, spanning room air, SkyAir, and VRV indoor equipment

Daikin A3: drain level control abnormality on the indoor unit

Daikin assigns A3 to the drain level control system in the indoor unit division of its malfunction chart. The control detected that the condensate level or the drain system response was outside normal, and it stopped operation to prevent the tray overflowing. The chart names the system, which is why A3 covers the float switch, the drain pump, and the path between them rather than any one of them. Applies to: Daikin indoor units covered by the SM-TS3 malfunction code chart, spanning room air, SkyAir, and VRV indoor equipment A3 is read from the Daikin After Sales Service malfunction code chart, which divides codes by unit rather than by model. The chart gives the meaning of the letter and detail code; the component layout behind it comes from the service manual for the specific indoor unit. A wall-mounted room air unit without a drain pump does not carry the same detection. Owner-safe checks: Select fan operation or switch the affected indoor unit off so the coil stops condensing while the fault is outstanding. | Record the unit number shown beside A3 and the room that unit serves, which identifies the address for service. | Check whether the external condensate discharge point produced any water during the period the unit had been cooling. Qualified technician: Opening a cassette decoration panel, testing a float switch, or clearing a drain pan inside the indoor unit is qualified service work on this equipment. | Any water that has reached ceiling material, lighting, or an electrical accessory is a stop condition, and the indoor unit should be isolated rather than restarted.

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F-series ProfessionalRequired
Cooper & Hunter • ductless-mini-split — Cooper and Hunter ductless mini-split systems documented in the Cooper and Hunter support library

Cooper and Hunter F codes: a sensing family shared across the range

Cooper and Hunter groups its sensing faults into an F-series, where the letter marks a temperature sensing problem and the digit identifies which sensor position the control was reading. Every entry in the family shares the same meaning at the level of the letter: a reading the control will not act on. Applies to: Cooper and Hunter ductless mini-split systems documented in the Cooper and Hunter support library Cooper and Hunter sells several ductless ranges and publishes documentation per range rather than as one list. The digit following the F identifies a sensor position within the model's own scheme, so the support document for your series is what maps it. Ranges from other suppliers using similar lettering are unrelated. Owner-safe checks: Photograph the display showing the complete code, letter and digit together, before power is interrupted. | Compare the temperature the indoor unit reports against a separate thermometer and note both figures. | Record which indoor unit is affected and whether any others on the system are behaving oddly. Qualified technician: Sensing elements, their connectors, and the harnesses linking them to the board sit inside casings that also carry mains supply, so access is qualified work. | An outdoor sensing fault can accompany water ingress into the enclosure, which needs assessing beyond the sensing element itself.

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E1 ProfessionalRequired
Cooper & Hunter • ductless-mini-split — Sophia multi-zone cassette indoor units

Cooper & Hunter Sophia cassette E1 communication error

For the documented Cooper & Hunter Sophia multi-zone cassette, E1 means the indoor and outdoor equipment are not communicating. It describes the failed control path, not a confirmed outdoor board failure; field wiring, terminals, pairing, supply, and both control ends still need to be proved. Applies to: Sophia multi-zone cassette indoor units This page applies only to the Sophia multi-zone cassette manual cited below. Cooper & Hunter sells several platforms whose identical E1 display can mean something else, so identify the series and indoor-unit style first. Owner-safe checks: Record the code, paired model numbers, whether the cassette ever worked, and the operating status of every other zone without removing covers. Qualified technician: Addressing, terminal, continuity, voltage, communication-signal, and board checks require an installer qualified for the Sophia multi-zone platform.

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34 ProfessionalRequired
Carrier • furnace — Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T

Carrier status code 34: ignition proving failed on this trial

Carrier lists status code 34 as an ignition-proving fault. It records that a trial for ignition did not end with a proven flame, and unlike code 14 it does not mean the control has given up. Seeing 34 without 14 means the furnace is still retrying, which is the moment when observing what happens is worth most. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T Read here from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. The relationship between the per-trial fault and the lockout that follows it is specific to this control family, and other manufacturers using the number 34 are not describing the same thing. Owner-safe checks: Listen to a full heating cycle from a safe distance and note whether a flame is established at all, and whether it is lost after establishing. | Keep a tally over several days of how many heat calls succeed and how many fail, with the times of day. | Confirm that other gas appliances behave normally and note whether failures coincide with their use. Qualified technician: Measuring the flame signal, testing igniter resistance, cleaning a sensing electrode, and checking manifold gas pressure are licensed gas-furnace tasks. | Any smell of gas requires the emergency response for your supplier before any further troubleshooting: leave the property, avoid switches, and call from outside.

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