Product error-code directory

Boilers and HVAC error codes

Search fault, warning and status codes for boilers, air conditioners, heat pumps, thermostats and ventilation equipment. Find quick meanings, model context, safe checks and available source guidance.

2,693documented codes
32manufacturers
30product groups

About Boilers and HVAC error codes

Error codes are diagnostic indicators generated when a product detects an operating condition outside its expected range. They help narrow the search, but they do not automatically prove that a named component has failed. The same code can have different meanings across manufacturers, products, model generations and regions.

This category directory covers boilers, air conditioners, heat pumps, thermostats and ventilation equipment. Start with the exact characters shown on the display, then confirm the manufacturer, product type and full model number. Every indexed result links to a dedicated page containing a quick answer, likely symptoms and causes, safe troubleshooting boundaries, reset guidance, applicable products and source information.

Do not repeatedly reset a returning fault or use instructions written for a different model. Isolate electrical products before accessible checks and stop where gas, refrigerant, high voltage, stored energy, hot components or moving machinery may be involved. Use an authorised technician whenever diagnosis requires covers to be removed or safety-critical systems to be tested.

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All Boilers and HVAC codes

Showing 2,601–2,693 of 2,693

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213Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomTemp difference between supply and return exceeding limitWorcester Bosch documents 213 for the Legacy Greenstar CDi, Si and i gas boilers as “Temp difference between…214Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFan shut down during safety timeWorcester Bosch documents 214 for the Legacy Greenstar CDi, Si and i gas boilers as “Fan shut down…219Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomSupply or return water too hotWorcester Bosch documents 219 for the Legacy Greenstar CDi, Si and i gas boilers as “Supply or return…2207Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomLow or missing PWM signal from circulation pumpWorcester Bosch documents 2207 for the Legacy Greenstar CDi, Si and i gas boilers as “Low or missing…222Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInterruption of the NTC cablingWorcester Bosch documents 222 for the Legacy Greenstar CDi, Si and i gas boilers as “Interruption of the…223Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlow temperature sensor wiring interruptedWorcester Bosch documents 223 for the Legacy Greenstar CDi, Si and i gas boilers as “Flow temperature sensor…224Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomSafety temp. limiter has trippedWorcester Bosch documents 224 for the Legacy Greenstar CDi, Si and i gas boilers as “Safety temp. limiter…227Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo flame signal after ignitionWorcester Bosch documents 227 for the Legacy Greenstar CDi, Si and i gas boilers as “No flame signal…228Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame signal detected without a flameWorcester Bosch documents 228 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame signal detected…229Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame failed during burner operationWorcester Bosch documents 229 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame failed during…232Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler locked by external switching contactWorcester Bosch documents 232 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler locked by…233Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler identification module or electronics faultWorcester Bosch documents 233 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler identification module…234Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas valve electrical faultWorcester Bosch documents 234 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas valve electrical…235Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomConflicting boiler electronics and identification versionsWorcester Bosch documents 235 for the Legacy Greenstar CDi, Si and i gas boilers as “Conflicting boiler electronics…237Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomSystem faultWorcester Bosch documents 237 for the Legacy Greenstar CDi, Si and i gas boilers as “System fault”. This…238Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler electronics faultWorcester Bosch documents 238 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler electronics fault”.…240Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomReturn temperature sensor wiring interruptedWorcester Bosch documents 240 for the Legacy Greenstar CDi, Si and i gas boilers as “Return temperature sensor…241Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomReturn temperature sensor wiring interruptedWorcester Bosch documents 241 for the Legacy Greenstar CDi, Si and i gas boilers as “Return temperature sensor…245Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomState outside permitted rangeWorcester Bosch documents 245 for the Legacy Greenstar CDi, Si and i gas boilers as “State outside permitted…249Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal software errorWorcester Bosch documents 249 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal software error”.…250Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomDefault software errorWorcester Bosch documents 250 for the Legacy Greenstar CDi, Si and i gas boilers as “Default software error”.…251Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlash memory test errorWorcester Bosch documents 251 for the Legacy Greenstar CDi, Si and i gas boilers as “Flash memory test…252Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomStack overflowWorcester Bosch documents 252 for the Legacy Greenstar CDi, Si and i gas boilers as “Stack overflow”. This…253Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomRAM test errorWorcester Bosch documents 253 for the Legacy Greenstar CDi, Si and i gas boilers as “RAM test error”.…254Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomEEPROM test errorWorcester Bosch documents 254 for the Legacy Greenstar CDi, Si and i gas boilers as “EEPROM test error”.…258Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal watchdog errorWorcester Bosch documents 258 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal watchdog error”.…259Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAD reference errorWorcester Bosch documents 259 for the Legacy Greenstar CDi, Si and i gas boilers as “AD reference error”.…262Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal operating-system errorWorcester Bosch documents 262 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal operating-system error”.…263Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomProgram sequence errorWorcester Bosch documents 263 for the Legacy Greenstar CDi, Si and i gas boilers as “Program sequence error”.…265Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat demand lower than energy suppliedWorcester Bosch documents 265 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat demand lower…268Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomRelay test activatedWorcester Bosch documents 268 for the Legacy Greenstar CDi, Si and i gas boilers as “Relay test activated”.…269Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame monitoring faultWorcester Bosch documents 269 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame monitoring fault”.…270Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler starting upWorcester Bosch documents 270 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler starting up”.…273Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBurner and fan operation interruptedWorcester Bosch documents 273 for the Legacy Greenstar CDi, Si and i gas boilers as “Burner and fan…275Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler electronics in test modeWorcester Bosch documents 275 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler electronics in…278Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomSensor test failed in hot-water and heating modesWorcester Bosch documents 278 for the Legacy Greenstar CDi, Si and i gas boilers as “Sensor test failed…283Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBurner startingWorcester Bosch documents 283 for the Legacy Greenstar CDi, Si and i gas boilers as “Burner starting”. This…284Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAir-gas ratio control valve openingWorcester Bosch documents 284 for the Legacy Greenstar CDi, Si and i gas boilers as “Air-gas ratio control…285Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomReturn temperature too highWorcester Bosch documents 285 for the Legacy Greenstar CDi, Si and i gas boilers as “Return temperature too…2908Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler electronics or basic-controller system faultWorcester Bosch documents 2908 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler electronics or…2910Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlue-system faultWorcester Bosch documents 2910 for the Legacy Greenstar CDi, Si and i gas boilers as “Flue-system fault”. This…2915Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFan continues running after post-purgeWorcester Bosch documents 2915 for the Legacy Greenstar CDi, Si and i gas boilers as “Fan continues running…2916Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas valve detected open during post-purgeWorcester Bosch documents 2916 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas valve detected…2920Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame-monitoring faultWorcester Bosch documents 2920 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame-monitoring fault”. This…2923Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomUnexpected feedback from modulating gas valveWorcester Bosch documents 2923 for the Legacy Greenstar CDi, Si and i gas boilers as “Unexpected feedback from…2924Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo feedback from gas valveWorcester Bosch documents 2924 for the Legacy Greenstar CDi, Si and i gas boilers as “No feedback from…2925Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas-valve feedback too lowWorcester Bosch documents 2925 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas-valve feedback too…2926Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas-valve feedback too highWorcester Bosch documents 2926 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas-valve feedback too…2927Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame failed during operationWorcester Bosch documents 2927 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame failed during…2928Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal errorWorcester Bosch documents 2928 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal error”. This…2930Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat-exchanger electronics or controller system faultWorcester Bosch documents 2930 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat-exchanger electronics or…2931Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomIllegal microcontroller instructionWorcester Bosch documents 2931 for the Legacy Greenstar CDi, Si and i gas boilers as “Illegal microcontroller instruction”.…2940Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomLow voltageWorcester Bosch documents 2940 for the Legacy Greenstar CDi, Si and i gas boilers as “Low voltage”. This…2946Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomIncorrect code plug detectedWorcester Bosch documents 2946 for the Legacy Greenstar CDi, Si and i gas boilers as “Incorrect code plug…2948Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo flame signal at low outputWorcester Bosch documents 2948 for the Legacy Greenstar CDi, Si and i gas boilers as “No flame signal…2949Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo flame signal at high outputWorcester Bosch documents 2949 for the Legacy Greenstar CDi, Si and i gas boilers as “No flame signal…2950Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo flame signal after starting procedureWorcester Bosch documents 2950 for the Legacy Greenstar CDi, Si and i gas boilers as “No flame signal…2951Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame lost too many timesWorcester Bosch documents 2951 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame lost too…2952Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal ionisation-signal test faultWorcester Bosch documents 2952 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal ionisation-signal test…2955Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat exchanger incompatible with hydraulic configurationWorcester Bosch documents 2955 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat exchanger incompatible…2956Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat-exchanger hydraulic configuration activeWorcester Bosch documents 2956 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat-exchanger hydraulic configuration…2957Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal control errorWorcester Bosch documents 2957 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal control error”.…2958Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAppliance-electronics system faultWorcester Bosch documents 2958 for the Legacy Greenstar CDi, Si and i gas boilers as “Appliance-electronics system fault”.…2959Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAppliance-electronics system faultWorcester Bosch documents 2959 for the Legacy Greenstar CDi, Si and i gas boilers as “Appliance-electronics system fault”.…2960Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAppliance-electronics system faultWorcester Bosch documents 2960 for the Legacy Greenstar CDi, Si and i gas boilers as “Appliance-electronics system fault”.…2961Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNo fan signalWorcester Bosch documents 2961 for the Legacy Greenstar CDi, Si and i gas boilers as “No fan signal”.…2962Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFan not runningWorcester Bosch documents 2962 for the Legacy Greenstar CDi, Si and i gas boilers as “Fan not running”.…2963Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlow and heat-exchanger sensor signals outside rangeWorcester Bosch documents 2963 for the Legacy Greenstar CDi, Si and i gas boilers as “Flow and heat-exchanger…2964Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat-exchanger flow rate too lowWorcester Bosch documents 2964 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat-exchanger flow rate…2965Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlow temperature too highWorcester Bosch documents 2965 for the Legacy Greenstar CDi, Si and i gas boilers as “Flow temperature too…2966Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat-exchanger flow temperature rising too rapidlyWorcester Bosch documents 2966 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat-exchanger flow temperature…2972Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomMains voltage too lowWorcester Bosch documents 2972 for the Legacy Greenstar CDi, Si and i gas boilers as “Mains voltage too…2973Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler electronics or controller system faultWorcester Bosch documents 2973 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler electronics or…2974Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomInternal faultWorcester Bosch documents 2974 for the Legacy Greenstar CDi, Si and i gas boilers as “Internal fault”. This…2980Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomSuper lockout after repeated resetsWorcester Bosch documents 2980 for the Legacy Greenstar CDi, Si and i gas boilers as “Super lockout after…2981Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler locked after repeated resetsWorcester Bosch documents 2981 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler locked after…305Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat exchanger in hot-water anti-cycle modeWorcester Bosch documents 305 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat exchanger in…306Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlame signal after fuel supply closedWorcester Bosch documents 306 for the Legacy Greenstar CDi, Si and i gas boilers as “Flame signal after…341Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomHeat-exchanger temperature rise too rapidWorcester Bosch documents 341 for the Legacy Greenstar CDi, Si and i gas boilers as “Heat-exchanger temperature rise…347Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomReturn temperature exceeds flow temperatureWorcester Bosch documents 347 for the Legacy Greenstar CDi, Si and i gas boilers as “Return temperature exceeds…351Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomFlow temperature sensor interruptedWorcester Bosch documents 351 for the Legacy Greenstar CDi, Si and i gas boilers as “Flow temperature sensor…353Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNon-volatile lockout testWorcester Bosch documents 353 for the Legacy Greenstar CDi, Si and i gas boilers as “Non-volatile lockout test”.…357Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomVentilation programme activeWorcester Bosch documents 357 for the Legacy Greenstar CDi, Si and i gas boilers as “Ventilation programme active”.…358Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomAnti-seizing function activeWorcester Bosch documents 358 for the Legacy Greenstar CDi, Si and i gas boilers as “Anti-seizing function active”.…360Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomIncompatible code plugWorcester Bosch documents 360 for the Legacy Greenstar CDi, Si and i gas boilers as “Incompatible code plug”.…362Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBoiler identification module or electronics faultWorcester Bosch documents 362 for the Legacy Greenstar CDi, Si and i gas boilers as “Boiler identification module…363Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomIonisation current did not drop during testWorcester Bosch documents 363 for the Legacy Greenstar CDi, Si and i gas boilers as “Ionisation current did…364Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas-valve solenoid EV2 leakingWorcester Bosch documents 364 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas-valve solenoid EV2…365Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomGas-valve solenoid EV1 leakingWorcester Bosch documents 365 for the Legacy Greenstar CDi, Si and i gas boilers as “Gas-valve solenoid EV1…522Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNTC drift test runningWorcester Bosch documents 522 for the Legacy Greenstar CDi, Si and i gas boilers as “NTC drift test…568Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomWater-pressure sensor disconnected or faultyWorcester Bosch documents 568 for the Legacy Greenstar CDi, Si and i gas boilers as “Water-pressure sensor disconnected…578Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomNTC temperature sensor damagedWorcester Bosch documents 578 for the Legacy Greenstar CDi, Si and i gas boilers as “NTC temperature sensor…604Worcester Bosch · Legacy Greenstar CDi, Si and i gas boilers · United KingdomBurner control-unit system faultWorcester Bosch documents 604 for the Legacy Greenstar CDi, Si and i gas boilers as “Burner control-unit system…