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    Worcester Bosch Boiler Fault Codes Guide

    Posted on 22nd January 2021 by H2 Property Services

    Is your Worcester-Bosch boiler displaying seemingly random letters and numbers? These are known as ‘fault codes’ or ‘error codes’.

    These codes appear when your boiler has experienced a fault, with each code representing a specific issue. You may be able to resolve some issues yourself, or you may need professional intervention from an experienced boiler engineer. Use this guide to find out your next steps to fixing your Worcester-Bosch boiler.

    Worcester Bosch Boiler Fault Codes

    Worcester Bosch Boilers

    If you need boiler services across London, use a boiler engineer that you can trust. H2 Property Services have been fixing boilers for over 15 years. All our engineers are gas-safe certified and can fix boilers from all the leading manufacturers. Using your boiler’s fault code and our wealth of experience, we will locate and fix any problems quickly. We even offer emergency call-outs if your boiler needs immediate attention. Simply get in touch and we’ll be there.

    For trusted boiler services in London, give our team a call today on 020 3858 8013. Or use our quick quote form!

    Find your Worcester Bosch Boiler Model:

     


     

    Worcester Bosch CDI Classic Combi Boiler Error Codes

     

    Fault Code Reason(s)
    A1 Water is leaking or the pump needs replacing or freeing due to the pump running dry.
    A7 The hot water negative thermistor coefficient (NTC) sensor is defective – the hot water sensor or connecting leads need checking.
    A8 Break communication to FX sensor controls electrical connections need checking.
    B1 Code plug not detected .
    C6 Fan speed too low – the fan lead and connector need checking and may need replacing.
    E2 Central heating (CH) water flow negative thermistor coefficient (NTC) sensor defective check CH flow NTC sensor and connection leads.
    E9 Safety temperature limiter in central heating (CH) flow has tripped the system pressure or safety temperature limiter needs checking
    EA Flame not detected due to a gas issue – the gas supply, power supply or igniter, electrode and lead need checking – contact a Gas Safe installer.
    F0 Internal error – electrical connector contacts or programmer interface module – check ignition leads are not loose.
    F7 Flame detected even though the appliance is switched off – check the electrode assembly is dry and the pcb and flue are clear.
    FA Flame detected after gas shut off – the gas valve needs checking – hire a Gas Safe installer.
    FD Reset button pressed by mistake – press reset button again.

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch CDI Highflow Combi Boiler Error Codes

     

    Fault Code Reason(s)
    A1 Pump dry run detection or pump is running in air the system pressure needs checking
    A5 Tank negative thermistor coefficient (NTC) defect
    A7 Domestic hot water (DHW) negative thermistor coefficient (NTC) defect
    A8 Energy Management System (EMS) communication error
    B1 Code plug not detected
    B2, B3, B4, B5, B6 Data error
    B7 Burner control error
    C6 Fan defect
    D3 External temperature limiter
    D5 Condensate pump failure
    D6 Internal heat bank overflow
    EA Flame not detected
    E2 Primary negative thermistor coefficient (NTC) defect
    E9 Safety temperature limiter in central heating (CH) flow stat tripped
    F0 Internal error
    F1 ROM fault
    F7 Flame detected after appliance has been shut off
    FA Flame detected after gas shut off
    FD Reset button pressed – try pressing the reset button again

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch CDi Compact / Greenstar 25/30 Si Combi / Greenstar 27/30 I system Boiler Error Codes

     

    Fault Code Reason(s)
    T1 Ignition test – checking the igniter spark
    T2 Fan test – checking the basic fan
    T3 Pump test – checking the basic pump
    T4 Three way valve test
    T6 Ionisation oscillator test
    9A 362 error – incorrect HCM fitted
    9U 233 Heat Control Module (HCM) error – problem with code plug
    B7 257 Internal error – possible control board problem
    C6 215 Fan problem – fan running too fast
    C7 214 Fan problem – fan not running
    D1 240 Return sensor error – sensor may be wet or damaged
    E2 222 Flow sensor short circuit error
    E5 218 Flow temperature too high
    E9 219 Safety sensor fault – temperature too high, sensor short circuit or open circuit
    EA 227 No flame detected or flame signal loss during operation
    F0 237 Internal error
    F7 228 Flame error – false flame or flame detected before burner started
    FA 306 False flame fault – flame detected after burner stop
    FD 231 Mains power fault – electrical power interruption
    FA 364 Gas valve EV2 leak test failed – gas valve leak
    FB 365 Gas valve EV1 leak test failed
    A1 281 Pump stuck or running with air in the system
    C1 264 Airflow stopped during operation
    C4 273 Airflow present during last 24 hour
    D1 240 Return sensor short circuit
    D4 271 Temperature difference between flow and safety sensor exceeds limit
    E9 224 Max thermostat activated – flue gas thermostat overheat
    EA 227 No ionisation detected after ignition
    EF 349 Central heating boil detected – boiler operating at minimum burner load with temperature difference greater than 18°C between Flow & Return.
    NO CODE 212 Safety or flow temperature rising too fast

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch CDi Classic Regular Boiler Error Codes

     

    Fault Code Reason(s)
    B1 Code plug not detected
    C6 Fan speed too low
    E2 Central heating (CH) flow negative thermistor coefficient (NTC) sensor defective
    E9 Safety temperature limiter in central heating (CH) flow has tripped
    EA Flame not detected
    F0 Internal error
    F7 Flame detected even though appliance switched off
    FA Flame detected after gas shut off
    FD Reset button pressed by mistake

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch Greenstar I System / Combi Boiler Error Codes

     

    Fault Code Reason(s)
    226 Service tool has been connected in the blocking error history menu
    FD 231 The power has been interrupted during a lockout
    C7 214 Fan does not run during the start up phase – fan harness connector needs checking
    C6 215 Fan speed too high – check the fan harness and connector
    C7 216 Fan speed too low – check the fan harness and connector
    C7 217 Fan has stopped during appliance operation
    C1 264 Fan stopped during operation
    C4 273 Continuous fan operation for the last 24 hours – appliance temporarily blocked
    E2 222 Flow temperature sensor shorted
    E2 233 Flow temperature sensor disconnected
    E9 276 Primary flow temperature exceeded 95°c
    E2 350 Flow temperature sensor shorted
    E2 351 Flow temperature sensor disconnected
    FA 306 Ionisation detected after the gas valve closed
    EA 227 No ionisation detected after ignition
    F7 228 Isioniation current detected before burner start
    EA 229 Loss of ionisation signal during operation
    EA 261 Heat control module (HCM) potentially defective – reset the appliance
    9U 233 Control box or heat control module (HCM) is defective or loose, the HCM needs to be checked
    C4 237 Control box or heat control module (HCM) is defective
    F0 238 Gas valve or control box error – gas valve coils need checking
    F0 239 Control box or the heat control module (HCM) is defective – the control box connections need checking
    F0 242 Control box or the heat control module (HCM) is defective – the HCM and control box connections need to be checked
    B7 257 Control box or the heat control module HCM) is defective- the HCM and control box connections need to be checked
    F0 258 Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
    EH 258 Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
    F1 259 Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
    F0 262 Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
    F1 263 Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
    F0 272 Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing
    F0 280 Control box or the heat control module (HCM) is defective – control box and connections need checking or HCM might not be inserted properly and need replacing
    F0 290 Control box is defective – HCM needs checking as it might not be inserted properly or need replacing
    328 Internal error with the mains voltage – frequency may be inconsistent
    235 Incompatible heat control module (HCM) software versions – control box needs latest software
    356 Low mains voltage – the voltage may be interrupted or inconsistent and needs checking
    360 Heat control module (HCM) invalid – the inserted HCM does not correspond with the control box
    A8 362 Low mains voltage – the voltage may be interrupted, inconsistent or heat control module (HCM) invalid
    CC 800 Outdoor sensor defect available when accessory outdoor sensor is connected
    A1 281 Pump stock or running dry
    E9 224 Flue or high limit thermostat activated
    D4 341 Primary flow temperature rising too fast

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch GB162 Boiler Error Codes

     

    Fault Codes Reason(s)
    208 The boiler is in chimney sweep mode
    200 The boiler is in heating mode
    201 The boiler is in domestic hot water (DHW) mode
    202 The boiler is waiting – there was a heat demand from the on off or modulating control
    203 The boiler is on standby
    204 The boiler is waiting – the actual temperature is higher than the calculated or selected boiler temperature
    212 The temperature recorded by the flow temperature sensor or the safety sensor is rising too quickly
    226 Diagnosis tool was connected and is now locked out
    260 The flow temperature sensor is not detecting a rise in temperature following a burner start
    265 The boiler is waiting in response to a heat demand – the boiler regularly switches to partial load
    268 Component test phase
    270 The boiler is modulating upwards
    283 The boiler is preparing for a burner start – the fan and pump are activated
    284 The gas valve is switched
    305 The boiler is waiting for domestic hot water (DHW) operation to end
    235 The KIM (boiler identification module) is too new for the burner control unit
    360 The KIM that has been fitted is not compatible with the burner control unit
    9A 361 The burner control unit that has been fitted is not compatible with the KIM (boiler identification module)
    9U 233 The burner control unit or KIM (boiler identification module) is faulty
    A3 317 Short circuit in the flue gas temperature sensor contacts
    B7 257 The burner control unit or the KIM (boiler identification module) is faulty
    C1 264 No control signal or power supply to the fan during operation
    C4 273 The boiler was switched off for a maximum of 2 minutes because it had been operating continuously for more than 24 hours
    C6 215 The fan speed is too high
    C6 216 The fan speed is too low
    C7 214 The fan does not run during the start phase
    C7 217 The fan speed is irregular when starting up
    CE 207 Water pressure is too low
    CE 266 Pump test failed
    D1 240 The contacts of the boiler return temperature sensor have been short circuited
    D1 241 The contacts of the boiler return temperature sensor have been interrupted
    D3 232 The external switching contact has opened
    D4 213 The actual temperature recorded by the flow temperature sensor or return temperature sensor is rising too quickly
    D4 271 Actual temperature differential between flow and safety temperature sensor is too high
    D4 286 The boiler return temperature sensor has detected a return temperature higher than 105°c
    E2 222 Short circuit in the flow temperature sensor contacts
    E2 223 The flow temperature sensor contacts have been interrupted
    E5 218 The temperature captured by the flow temperature sensor exceeded 105°c
    E9 210 The temperature measured by the flue gas sensor is too high and is open
    E9 219 The safety temperature sensor has captured a temperature in excess of 105°C
    E9 220 The contacts for the safety temperature sensor have shorted or the safety temperature sensor has detected a temperature higher than 130°c
    E9 224 The contacts of the safety temperature sensor have been interrupted
    E9 276 The temperature flow sensor has measured a temperature in excess of 95°c
    E9 277 The safety temperature sensor has measured temperature in excess of 95°c
    E9 285 The boiler return temperature sensor has measured a temperature higher than 95°c
    E9 318 The flue gas temperature sensor contacts have been interrupted
    EA 227 An insufficient ionisation current was measured following ignition of the burner
    EA 229 The ionisation current detected by the system during the burning phase was insufficient
    EA 234 The contacts of the gas valve have been interrupted
    EA 261 The burner control unit is faulty
    EA 269 The ignition device has been activated for too long
    F0 238 The burner control unit KIM (boiler identification module) is faulty
    F0 239 The burner control unit KIM (boiler identification module) has an error. Cabling might have poor contact breaks and pinching or the plug and wiring of the burner control unit needs checking, also check the operating characteristics of the boiler by replacing the burner control unit.
    F0 242, F0 243, F0 244, F0 245,F0 246, F0 247,
    F0 248, F0 249, F0 250, F0 251, F0 252, F0 253,
    F0 255, F0 259, F0 263, F0 267, F0 272
    The burner control unit (KIM) is faulty – the wiring of the burner control unit needs checking, also check the operating characteristics of the boiler by replacing the burner control unit.
    F0 278 The sensor test has failed – cabling and plug sensors need checking
    F0 279 The burner control unit, or KIM, is faulty – control unit may need replacing
    F0 280 The burner control unit is faulty
    F0 287 The burner control unit, or KIM, has an error
    F0 290 The burner control unit, or KIM, is faulty
    F7 228 An ionisation current was measured before the burner started
    F7 328 A brief power failure has occurred
    FA 306 An ionisation current was measured after the burner went out
    FD 231 The mains voltage was interrupted during an interlocking fault
    EC 256 The burner control unit has an error
    EH 258 The burner control unit is faulty – check the plug and wiring of the burner control unit.
    H07 The current water pressure is too low, limiting the performance in heat mode as well as domestic hot water (DHW) mode
    HrE The boiler keeps resetting
    rE The boiler resets

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch CDI Highflow Combi Boiler Error Codes

     

    Fault Code Reason(s)
    Light off No boiler demand
    Light on Heating demand on boiler is OK
    1 flash 5 seconds off No ionisation detected after ignition
    2 flashes 5 seconds off Loss of ionisation signal during operation
    3 flashes 5 seconds off Gas valve error
    4 flashes 5 seconds off First safety timing error / ignition timing error
    5 flashes 5 seconds off Ionisation detected after burner stopped
    Gas valve EV2 leak test failed
    Gas valve EV1 leak test failed
    Ionisation current detected before burner start
    Gas valve error
    Ionisation sensor shorted
    4 flashes 5 second gap 1 long flash Sensor test failed
    4 flashes, 5 second gap, 2 long flashes Safety temperature too high
    4 flashes, 5 second gap, 3 long flashes Max safety thermostat activated
    4 flashes, 5 second gap, 4 long flashes Return temperature too high
    4 flashes, 5 second gap, 5 long flashes Flow temperature too high – supply sensor exceeded 110°c
    1 long flash, 4 quick flashes,
    5 second gap, 1 long flash, 4 quick flashes
    Heating control module (HCM) defective
    2 long flashes, 4 quick flashes, 5 second gap,
    2 long flashes, 4 quick flashes
    Fan running too fast
    Fan running too slow
    No airflow after defined period of time
    Fan not running
    3 long flashes, 4 quick flashes, 5 second gap,
    3 long flashes, 4 quick flashes
    Mains voltage interrupted after locking error
    4 long flashes, 4 quick flashes, 5 second gap,
    4 long flash, 4 quick flashes
    Internal control board faults
    5 long flashes, 4 quick flashes, 5 second gap,
    5 long flash, 4 quick flashes
    All other miscellaneous faults – reset the boiler by turning the control knob anti-clockwise to the reset position

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch Greenstar Ri Boiler Error Codes

     

    Fault Code Reason(s)
    No light No power at control board
    Light on Appliance on but not operating during demand
    Slow flash
    (mostly off flashes on)
    Ignition lockout
    Slow flash
    (mostly on flashes off)
    Flue overheat or heat exchanger overheat
    Fast flash Volatile lockout sensor fan or code plug
    2 pulses Check service mode switch is in minimum position
    5 pulses Check service mode switch is in max position

     

    Need help with your Boiler? Call our Boiler Engineers on 020 3858 8013!

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    Worcester Bosch Greenstar 8000 Boiler Error Codes

     

    Fault Code Reason(s)
    200 O Boiler in heating mode
    201 O Boiler in hot water mode
    202 O Boiler in anti-cycle mode
    203 0 Boiler in standby – no heat energy demand
    204 O Current primary water temperature higher than set value
    208 0 Chimney sweep demand
    224 V Safety temperature limiter has tripped – top-up water until the reset pressure is reached
    227 V No flame signal after ignition burner control unit could need replacing
    228 V Flame signal without flame present – air/gas ratio control valve may need replacing as might the ionisation cable
    305 0 Boiler in hot water anti-cycle mode
    306 V Flame signal after closing the fuel supply – the air/gas ratio control valve might need replacing
    360 V Incompatible code plug – check if a correct code plug is installed and exchange or reconnect code plug
    815 W/B Low loss header temperature sensor faulty – check the sensor port or check the differential sensor for incorrect installation position or breakage
    1010 O No BUS communication cable, EMS-Bus isn’t connected or damaged – connect the cable for the EMS-Bus or replace the damaged cable exchange fuse
    1017 W Water pressure too low – the water needs topping up and the vent system or pressure sensor may need replacing
    1021 B Hot water temperature sensor is defective – the plug to the hot water temperature sensor may not be connected
    1022 B Hot water storage temperature sensor is defective – connect the plug to the hot water temperature sensor correctly, mount the hot water temperature sensor correctly or replace the hot water temperature sensor
    1037 W Outside temperature sensor is defective – check the connecting lead
    1065 B Pressure sensor defective or not connected – check pressure sensor connection as it may need replacing
    1068 W Outside temperature sensor defective – check the connecting lead
    1073 W Short circuit of the flow temperature sensor – the temperature sensor may need replacing
    1074 W No signal from the flow temperature sensor available – connect the plug to the flow temperature sensor correctly or temperature sensor could need replacing
    1075 W Short circuit of the temperature sensor at the heating block – temperature sensor may need replacing
    1076 W No signal from the temperature sensor at the heating block available – replace the temperature sensor, the connecting lead or the control unit
    2920 V Error with the flame monitoring
    2924 V No feedback from the modulating gas valve. The gas valve relay is defective – press the reset button and apply burner start, wait to see if fault reoccurs, if it does the gas valve needs replacing
    2925 V Feedback from the modulating gas valve is too low
    2927 B Flame failed during burner operation. Open the main shut off valve, shut down the appliance and check gas line, replace the ionisation electrode, set burner correctly and minimum rated load, check the integrity flue system and if the interconnected room air supply is too small, or the size of the ventilation opening is too small, clean the heating block on the flue gas side or replace the control unit/burner control unit
    2946 V Incorrect code plug detected – the code plug needs replacing
    2948 B No flame signal. With low output the burner starts automatically after cleaning. If the fault occurs repeatedly, the setting of the CO2 valves need checking
    2950 B No flame signal. Following starting procedure the burner starts automatically. After cleaning set the correct gas / air ratio correctly
    2963 B Signal from flow and heat exchanger temperature sensor outside the permissible range – the connecting lead needs connecting correctly
    2964 B Flow rate in heat exchanger is too low
    2965 B Flow temperature too high
    2966 B Flow temperature rise in heat exchanger too rapid
    2967 B Flow / heat exchanger temperature sensor differential too great
    2970 B Pressure drop in heating system too rapid
    2971 B System pressure too low – the heating system needs venting or water needs topping up until the preset pressure is reached. Replace the cable to the pressure sensor replace the pressure sensor

     

    Worcester Bosch Error Code EA 229 or D5

    If you’re seeing the error code EA 229 or D5 on your Worcester Bosch boiler, this means that the condensate pipe is frozen. This happens due to the condensate pipe running outside.

     

    Worcester Bosch Boiler Engineers London

    Our knowledge and exposure to all the different makes and models means that they are quickly able to diagnose faults and correctly identify parts for replacement. Our specialists can also make long-lasting repairs and carry out effective maintenance services.

    This helps to ensure the length-of-life of your boiler is extended as long as possible. This allows us to pass on to our customers extended warranties of up to 8 years for their new boilers. We are experienced with all makes and models of boilers, and our friendly team are always happy to help.

    Contact our team today on 020 3858 8013 for a quote.

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