ErrorLookupHub Appliance Diagnostics
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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
33 ProfessionalRequired
Carrier • furnace — Carrier 58MCB Series 110 and 120 condensing gas furnaces

Carrier 58MCB code 33: limit circuit fault is two different warnings

Carrier 58MCB status code 33 means the limit circuit is open. That circuit includes the high-limit switch and flame-rollout switches, so the code does not tell you which safety opened. Check only the filter and unobstructed grilles; visible flame rollout, soot, a gas odor, or a returning code requires immediate service. Applies to: Carrier 58MCB Series 110 and 120 condensing gas furnaces This interpretation is limited to the Carrier 58MCB Series 110 and 120 manual. Other Carrier furnace controls can use the same number with different timing or component groupings, so confirm the model on the furnace rating plate. Owner-safe checks: With the furnace off, inspect only the normal homeowner-access filter and replace it with the specified size and type if loaded. | Confirm return grilles and supply registers are open and clear without reaching into ducts or removing furnace panels. | Record the full flash pattern, operating sequence, and any later code before power is interrupted. Qualified technician: Identifying the open device, measuring temperature rise, testing safeties, and inspecting combustion require licensed gas-furnace service. | A rollout indication, soot, gas odor, or carbon-monoxide alarm is a stop condition, not a reset opportunity.

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32 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 32: three switches share one number

Carrier writes status code 32 as the low-heat pressure switch, the draft safeguard switch, or the downflow auxiliary limit switch failing to close or reopening after it had closed. Three separate devices share the entry, and the control cannot tell you which one acted, so the code narrows the fault to a group rather than to a part. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T Guide 58-3T is the source here, and it covers deluxe two-stage induced-combustion equipment only. The auxiliary limit named in the entry is present on downflow arrangements, so what the code can mean depends on how your furnace is installed as well as on which model it is. Owner-safe checks: Look at the outdoor vent and intake terminations from ground level and note any ice, snow, nesting material, or vegetation without attempting to clear anything at height. | Time how long the furnace produces heat before it stops, and whether the burners lit at all. | Keep a short log of the outdoor temperature and wind conditions each time the code appears. Qualified technician: Measuring draft pressure, inspecting the vent system, clearing condensate traps, and testing pressure switches are licensed gas-furnace tasks. | Combustion products detected indoors, or a carbon monoxide alarm sounding, outranks every other instruction on this page. Get people out, open up the space, and call the emergency line your gas supplier publishes.

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31 ProfessionalRequired
Carrier • furnace — Carrier two-stage and variable-speed modulating condensing furnaces that report status code 31

Carrier furnace status code 31: pressure switch did not close

Carrier assigns status code 31 to a high-heat pressure switch input that did not close when the control called for high or intermediate heat, or that opened during the heat cycle. It reports the state of a proving circuit, so the draft inducer, venting, condensate, tubing, wiring, and the switch itself all stay on the list until one is confirmed. Applies to: Carrier two-stage and variable-speed modulating condensing furnaces that report status code 31 This reading follows Carrier service literature for two-stage and modulating condensing furnaces that flash a two-digit status code. Single-stage models and other code numbers behave differently, and the legend printed inside the furnace door is what confirms the meaning for a given board. Owner-safe checks: With the furnace off, clear any frost, ice, snow, or debris from the outdoor vent and intake terminations and confirm the terminations are not obstructed. | Check the furnace filter is clean, the return and supply grilles are open, and the furnace access door is fully closed. Qualified technician: Measuring inducer pressure, testing the switch and inducer, clearing the condensate trap, and any wiring or gas-valve work require a qualified heating technician, and the pressure switch must never be bypassed.

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24 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 24: the secondary voltage fuse is open

Carrier defines status code 24 as the secondary voltage fuse being open. That fuse protects the 24-volt control circuit, and the guide specifies a 3 amp automotive blade type that must be replaced only with another 3 amp fuse. A fuse opens because something drew more current than the circuit allows, so the fuse is the symptom. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, per troubleshooting guide 58-3T The fuse rating and the code definition come from Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Fuse ratings differ between control platforms, and fitting anything other than the rating in the literature for your exact model removes the protection the circuit was designed around. Owner-safe checks: Establish exactly what has stopped: heating alone, heating and cooling together, or any accessory such as a humidifier. | Check whether the thermostat display is blank or still powered, since that alone tells the technician which side of the circuit lost supply. | Write down any recent work on thermostats, cabling, outdoor equipment, or the building fabric in the weeks beforehand. Qualified technician: Locating a short in the 24-volt circuit, testing the transformer, and replacing the control fuse are tasks inside an enclosure that also carries line voltage, so they belong to a qualified technician. | Never fit a fuse of a higher rating than the literature specifies. The protection the original rating provides is the reason the transformer and board survived the fault.

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16 ProfessionalRequired
Carrier • ducted-split — Carrier Infinity System Control paired with communicating equipment, with the outdoor-unit code structure documented for 24VNA6 and 25VNA4 variable-speed units

Carrier Infinity code 16 with 53, 55 or 47: telling a communication fault from a failed sensor

Read the number as a pair before deciding anything. On 24VNA6 and 25VNA4 equipment the outdoor board reports a base code plus an expansion code, so 16, 53 and 55 occupy different columns of one table and carry different meanings depending on the column they came from. A genuine loss of communication with the Infinity System Control sets no diagnostic fault at the outdoor unit: the service manual says the Comm light goes off and the equipment falls back to its discrete control inputs. Applies to: Carrier Infinity System Control paired with communicating equipment, with the outdoor-unit code structure documented for 24VNA6 and 25VNA4 variable-speed units The code structure described here is the one published for the 24VNA6 and 25VNA4 outdoor units. Carrier furnaces, fan coils and older Infinity outdoor sections keep their own tables, and a two-digit number copied from one of those is not evidence about a variable-speed unit carrying this board. Owner-safe checks: Photograph the wall control message, the outdoor display, and the state of the Comm light before any power is interrupted. | Write down whether the number appeared in a code position or in a temperature field on a status screen. | Note which modes the system still accepts, because a mode that runs is evidence about what the control is protecting. Qualified technician: Resistance measurement at the control board connector, and any inspection inside the outdoor cabinet, is qualified service work. | Tracing the communication path between the outdoor board and the Infinity System Control involves energised low-voltage wiring and belongs to a technician.

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

Carrier status code 14: ignition lockout after four failed trials

Status code 14 on this Carrier control is ignition lockout. The guide states that lockout occurs after four consecutive unsuccessful trials for ignition and that the control resets itself automatically after three hours. The number 14 therefore counts failures; it does not identify which part of the ignition sequence failed. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, covered by troubleshooting guide 58-3T The count of four trials and the three-hour automatic reset are stated in Carrier troubleshooting guide 58-3T for deluxe two-stage induced-combustion furnaces. Single-stage and modulating Carrier controls, and the same number on other manufacturers, follow their own literature and their own retry counts. Owner-safe checks: Confirm that other gas appliances in the property are working normally, which separates a supply-wide interruption from a furnace-specific fault. | Check that the thermostat is calling for heat and that its batteries, if fitted, are good, so a failed call is not mistaken for a failed ignition. | Note the time of each lockout and the weather conditions, then leave the furnace off rather than forcing repeated retries. Qualified technician: Measuring gas pressure, testing igniter resistance, cleaning or replacing a flame sensor, and inspecting venting are licensed gas-furnace tasks. | A smell of gas at any point is an emergency. Leave the property, avoid switches and flames, and contact the emergency number for your gas supplier before anything else.

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

Carrier status code 13: the lockout that follows a limit or rollout switch

Carrier lists status code 13 as a limit or flame rollout switch lockout. The control had already seen that circuit open, reported it, and then decided the condition had lasted long enough to stop trying. A lockout is a deliberate refusal to restart, so code 13 is a stronger statement than the open-circuit code that precedes it. Applies to: Carrier deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors, as covered by troubleshooting guide 58-3T This reading is taken from Carrier troubleshooting guide 58-3T, which covers deluxe two-stage gas-fired induced-combustion furnaces with PSC or ICM blower motors. Other Carrier furnace controls, and the same numbers on Bryant or Payne equipment, are read from their own literature. Confirm the model on the furnace rating plate first. Owner-safe checks: With the furnace switched off, inspect the return-air filter and fit a clean one of the specified size and type if it is loaded. | Walk the house and confirm that supply registers and return grilles are open and not covered by furniture, rugs, or stored items. | Record the flash pattern through the sight glass without opening the blower door, along with the date and time of the lockout. Qualified technician: Identifying which safety device opened, measuring temperature rise, and inspecting combustion and venting are licensed gas-furnace tasks. | Treat soot, scorching, an odour of combustion products, or a carbon monoxide alarm as an immediate stop. Get fresh air into the space, keep the appliance off, and use the emergency number your gas supplier publishes.

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Communication loss ProfessionalRequired
Bryant • controls-thermostats — Bryant Evolution communicating systems using the Evolution Connex control and a four-conductor communication bus

Bryant Evolution communication loss: when the system stops talking to itself

A Bryant Evolution system is not a thermostat with switched wires. The control, the indoor unit, and the outdoor unit exchange data over a shared bus, and losing that conversation stops coordinated operation even when every individual component is healthy. A communication message therefore points at the path between devices before it points at any device. Applies to: Bryant Evolution communicating systems using the Evolution Connex control and a four-conductor communication bus This describes the communicating architecture Bryant uses for Evolution systems. A Bryant system with a conventional thermostat and individually switched conductors does not behave this way, and the Carrier equivalent of the same architecture carries its own message set. Confirm you have a communicating control before applying it. Owner-safe checks: Write down the exact message the wall control shows, including any number or reference it displays alongside it. | Establish whether heating or cooling still happens at all, and whether output varies or sits at one fixed level. | Note any recent storms, flooding, landscaping, or building work near the outdoor unit or the cable route between units. Qualified technician: Testing a communication bus, inspecting outdoor terminal blocks, and replacing damaged interconnecting cable are tasks inside enclosures carrying line voltage. | Do not substitute a conventional thermostat for a communicating control to restore operation. The equipment expects data on those conductors, not switched voltage.

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Prefix and digits ProfessionalRequired
Bosch • ductless-mini-split — Bosch Climate 5000 ductless mini-split systems documented in the Bosch service and manual library

Bosch Climate 5000: reading a code that names an indoor or outdoor origin

Bosch Climate 5000 codes are built from a prefix and a pair of digits, and the prefix carries real information: it says whether the indoor unit, the outdoor unit, or the link between them raised the condition. Reading the prefix first narrows a search that would otherwise begin with the digits and end in the wrong table. Applies to: Bosch Climate 5000 ductless mini-split systems documented in the Bosch service and manual library The Climate 5000 name covers single-zone and multi-zone equipment across more than one generation, and code assignments differ between them. Match the prefix and digits against the manual for the indoor and outdoor models on your data plates rather than against a chart for the range as a whole. Owner-safe checks: Photograph the indoor display so that the prefix and the digits are both captured together. | Copy the indoor and outdoor model numbers from their data plates before searching anything. | List any building work, decorating, or trades activity near the pipework or its cable route in recent months. Qualified technician: Interconnecting cable on this equipment carries mains voltage between the units, so inspecting, testing, or reterminating it is qualified work. | Outdoor protections reported through the indoor display involve the refrigerant circuit, which is certified activity rather than an owner check.

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PC 30 / PC 31 ProfessionalRequired
Bosch • multi-zone — Climate 5000 Generation 3 R-454B multi-zone outdoor units

Bosch PC 30 and PC 31: codes that exist on three outdoor models

PC 30 is high pressure protection and PC 31 is low pressure protection, and the service manual restricts both to three named outdoor units. An outdoor unit outside that list has no pressure switches to report on and will show a different code instead. Applies to: Climate 5000 Generation 3 R-454B multi-zone outdoor units The code table here is from the Bosch Climate 5000 Generation 3 R-454B multi-zone service manual dated May 2025, which covers the outdoor units. Indoor codes are published in the indoor service manual, and earlier Climate 5000 generations on a different refrigerant platform have their own documentation. Owner-safe checks: Record the full outdoor model number from the data plate and check it against the three models these codes are published for. | Photograph the code exactly, since the prefix and the final character both change the meaning. | Note the outdoor temperature, the mode, and how long the system had been running when it stopped. Qualified technician: Pressure measurement requires gauges on service ports and a certified technician, and this refrigerant platform has its own handling requirements. | Do not restart repeatedly against a protection code, since each attempt returns the system to the condition that stopped it.

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EC 07 ProfessionalRequired
Bosch • ductless-mini-split — Climate 5000 Generation 3 R-454B multi-zone

Bosch Climate 5000 EC 07 outdoor fan speed fault

On Bosch Climate 5000 Generation 3 R-454B multi-zone equipment, EC 07 means the outdoor fan speed is outside the control's expected range. The service procedure considers fan obstruction and assembly, motor wiring and feedback, the motor itself, and the outdoor PCB; the code does not select one of them. Applies to: Climate 5000 Generation 3 R-454B multi-zone This code definition applies only to the May 2025 Climate 5000 Gen 3 R-454B multi-zone manual. Earlier R-410A Climate 5000, single-zone, IDS, boiler, and Compress products use different references. Owner-safe checks: With the unit off, document EC 07, the exact outdoor model, guard and clearance condition, ice, and fan behavior from outside the cabinet. Qualified technician: Fan access, motor resistance and feedback, harness, live inverter-board, refrigerant, and R-454B safety checks require qualified Bosch service.

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E1 ProfessionalRequired
Blueridge • ductless-mini-split — BMKH floor-ceiling indoor units

Blueridge BMKH E1: compressor high pressure protection

Blueridge assigns E1 on this range to compressor high pressure protection. The control has stopped the compressor because pressure on the high side reached a limit, which is a protective action rather than a component failure. Applies to: BMKH floor-ceiling indoor units This meaning comes from the code table in the Blueridge BMKH floor-ceiling manual dated December 2023. Blueridge publishes different tables for its other indoor styles, and E1 on another manufacturer's ductless equipment routinely means something unrelated, so match the model plate before using this page. Owner-safe checks: Record whether the code appeared in cooling or in heating, and the outdoor conditions at the time. | Clear stored items, planting, and debris away from the outdoor cabinet so air can reach and leave the coil. | Check the indoor filter and the space in front of the unit, and confirm the fan is not left on its lowest setting. Qualified technician: Pressure measurement requires gauges on service ports and belongs to a certified technician. | Do not restart repeatedly against a protection code, because each attempt drives the system back toward the limit that stopped it.

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BMKH code groups ProfessionalRequired
Blueridge • ductless-mini-split — Blueridge BMKH ductless mini-split systems documented in the Blueridge manual library

Blueridge BMKH codes: a distributor brand with real documentation

Blueridge publishes documentation per indoor unit style as well as per series, so a wall-mounted BMKH and a floor console BMKH carry different manuals. Reaching for the right one matters because indoor-side entries relate to hardware that differs between those styles even within the same model family. Applies to: Blueridge BMKH ductless mini-split systems documented in the Blueridge manual library Blueridge is a distributor brand whose equipment is documented under its own manuals rather than under the manufacturer that builds it. Those manuals are the reference, and documentation for visually similar equipment sold under another name is not a substitute. Owner-safe checks: Identify the indoor unit style and find the manual issued for that style rather than for the series in general. | Photograph the displayed code and both model numbers before interrupting power. | Switch to fan mode if condensate is visible, so the coil stops producing water while the fault is outstanding. Qualified technician: Condensate pumps, sensing elements, and fan assemblies sit inside indoor casings that also carry the supply, which makes access qualified work. | Conditions raised by the outdoor unit involve the refrigerant circuit and the drive, and both require certification to work on.

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E160 ProfessionalRequired
Baxi • boiler — Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material

Baxi E160: fan or fan wiring, and why the boiler will not compromise

Baxi publishes E160 as a fan or fan wiring fault. Two distinct situations sit inside that phrase: a fan that is not turning at all, and a fan that is turning but whose speed the control cannot confirm. Both stop the boiler, and telling them apart from outside the casing starts with whether you can hear anything. Applies to: Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material The E-series codes are published by Baxi across several domestic ranges, and the same number does not necessarily carry the same detail on every one. Read it against the list on the label behind your own casing flap, and treat lists compiled for other manufacturers as unrelated. Owner-safe checks: Stand near the boiler during one start attempt and note whether any fan sound occurs, and for how long. | Write the code down exactly, since Baxi E-series numbers are three digits and adjacent numbers mean different things. | Think back over the last few months for anyone who has worked on the appliance or the circuits feeding it, and note what they did. Qualified technician: Fan testing, wiring inspection, and fan replacement on a room-sealed gas appliance are Gas Safe registered tasks in the United Kingdom. | Leave the front of the appliance exactly as it is. That panel is part of the sealed enclosure separating combustion from room air, and it is not an inspection hatch.

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E133 ProfessionalRequired
Baxi • boiler — Baxi domestic boilers covered by the manufacturer E133 guidance

Baxi E133: failed ignition and the frozen-condensate clue

Baxi defines E133 as a failed ignition condition. In freezing weather, a blocked frozen condensate pipe can contribute on installations with an external condensate run, but E133 is not a frozen-pipe detector. Fuel supply, ignition, flame proof, condensate, venting, and controls remain professional diagnostic branches. Applies to: Baxi domestic boilers covered by the manufacturer E133 guidance This guidance applies only to Baxi boilers whose own user or service instructions list E133. Product generation, country, and fuel setup matter; confirm the complete model before using any reset or thawing instruction. Owner-safe checks: Confirm the full model and weather, check other gas appliances, and inspect only an easily accessible ground-level external condensate section. Qualified technician: Inaccessible or internal condensate, recurring freezing, gas supply, ignition, electrode, combustion, vent, flame-proof, and sealed-case work require Gas Safe service.

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E119 ProfessionalRequired
Baxi • boiler — Baxi and Potterton domestic boilers that display E119

Baxi E119 fault code: low system pressure and how to clear it

Baxi assigns E119 to low water pressure in the heating system, below the level the boiler needs to operate. It is cleared by repressurising to between 1 and 1.5 bar with the filling device fitted to the boiler, and it points to a leak only if the pressure will not stay up afterwards. Applies to: Baxi and Potterton domestic boilers that display E119 This covers Baxi and Potterton boilers whose published fault guidance lists E119. Baxi uses E118 for a related low-pressure condition on some models, so match the exact digits, and confirm the boiler model before choosing a filling method. Owner-safe checks: With the boiler off, read the gauge and, if it is low, admit water with the boiler filling device until it reads 1 to 1.5 bar cold, then close the device fully. | Keep a short note of each repressurise, the date, and the pressure before and after, so a repeat loss can be measured. Qualified technician: A pressure that will not hold, visible damp or staining, a dripping outside overflow pipe, or any expansion vessel or internal check needs a Gas Safe registered engineer.

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E110 ProfessionalRequired
Baxi • boiler — Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material

Baxi E110: the overheat lockout that is really a circulation message

Baxi uses E110 for an overheat condition, where the boiler has exceeded its permitted maximum temperature or the safety thermostat has tripped. The measurement is genuine, but heat only accumulates when something stops carrying it away, so the investigation belongs to the water side of the system more often than to the burner. Applies to: Baxi domestic gas boilers using the E-series fault codes listed in Baxi support material Baxi publishes E-series codes across several domestic ranges, and the detail behind a number can differ between them. The list on the label behind the casing flap of your own appliance governs, and a Potterton or Main boiler from the same group carries its own published list even where components are shared. Owner-safe checks: Check the system pressure gauge on the boiler and write down the reading while the system is cold. | Feel every radiator after a heating attempt and record which warm up, which stay cold, and where on the panel the cold begins. | Note any noise from the boiler and whether it coincides with firing, and stop using the heating if kettling is present. Qualified technician: Pump testing and replacement, venting a sealed primary circuit, cleaning or flushing a system, and resetting a tripped safety thermostat are Gas Safe registered tasks. | A boiler that boils audibly should not be run while waiting for an appointment, because each episode damages the heat exchanger surface further.

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501 ProfessionalRequired
Ariston • boiler — Clas One and Clas System One condensing gas boilers

Ariston Clas One error 501: no flame detected

On the documented Ariston Clas One family, error 501 is a non-volatile lockout because flame was not detected. The boiler does not restart automatically and the user manual permits reset-button attempts, capped at five within 15 minutes. A returning 501 requires authorised technical service, not continued resetting. Applies to: Clas One and Clas System One condensing gas boilers This definition applies to Clas One and Clas System One user literature linked by Ariston. Nimbus heat pumps, Nuos water heaters, other One-series generations, and regional gas configurations need their own manual. Owner-safe checks: Photograph 501 and the model, check whether other gas appliances operate, and observe sounds only from outside the sealed case. Qualified technician: Gas supply pressure, valve, ignition, burner, flame signal, electrode, grounding, flue, condensate, control, and sealed-case work require authorised qualified service.

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108 ProfessionalRequired
Ariston • boiler — Ariston Clas ONE, Clas System ONE, and Alteas ONE boilers showing 108

Ariston 108 error code: refill request for low system pressure

Ariston shows 108 when the heating circuit pressure has fallen below the level the boiler needs, and it is asking for a refill. The owner opens the filling taps under the boiler until the gauge reads 1.0 to 1.5 bar cold, closes them, then clears the code with the reset control. A drop again within days points at a leak. Applies to: Ariston Clas ONE, Clas System ONE, and Alteas ONE boilers showing 108 This applies to Ariston Clas and Alteas family boilers whose user documentation lists 108 as a filling request. Ariston uses separate codes for a faulty pressure transducer, so if the gauge is already in band and 108 stays, treat it as a sensor branch and call an engineer. Owner-safe checks: With the boiler cold, open both filling taps under the boiler slowly until the gauge reads 1.0 to 1.5 bar, then turn both taps fully off and press reset once. | Note whether 108 clears after the reset and whether the pressure is still in band the next morning. Qualified technician: A pressure that will not hold, 108 showing with the gauge already in band, a suspected transducer fault, or any check inside the boiler casing needs a Gas Safe registered engineer.

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1-series ProfessionalRequired
Ariston • boiler — Ariston Clas gas boilers whose fault codes are grouped by leading digit in the Ariston user documentation

Ariston Clas overheat codes: the 1-series group and what it points at

Ariston organises Clas fault codes into groups by their leading digit, and the 1-series belongs to the primary water circuit. An overheat entry within that group therefore comes pre-labelled as a water-side condition, which is a genuinely useful piece of structure that most manufacturers do not offer. Applies to: Ariston Clas gas boilers whose fault codes are grouped by leading digit in the Ariston user documentation The grouping described here is the one Ariston uses in Clas user documentation. Ariston sells other ranges with their own conventions, and appliances sold under related brand names are documented separately. Match the code to the manual issued with your own boiler before applying the grouping. Owner-safe checks: Record all three digits of the code exactly, since the leading digit and the pair that follow it do different jobs. | Read the system pressure gauge while the system is cold and write the figure down. | Feel each radiator after a heating attempt and map which heat, which do not, and where the cold begins on the panel. Qualified technician: Anything that restores flow through a sealed heating circuit, from a new circulator to a chemical clean, is Gas Safe registered work when it involves the appliance itself. | A boiler making boiling or knocking sounds should be left off rather than run while waiting, because those episodes deposit scale on the exchanger surface.

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