Boiler Error Codes

    • Worcester Bosch

      Worcester Bosch CDI Classic Combi Boiler Error Codes

      Fault Description  System Behaviour
      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.

      Worcester Bosch CDI Highflow Combi Boiler Error Codes

      Fault Description System Behaviour
      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

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

      Fault Description System Behaviour
      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

      Worcester Bosch CDi Classic Regular Boiler Error Codes

      Fault Description System Behaviour
      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

      Worcester Bosch Greenstar I System / Combi Boiler Error Codes

      Fault Description System Behaviour
      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

      Worcester Bosch GB162 Boiler Error Codes

      Fault Description System Behaviour
      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
      Worcester Bosch CDI Highflow Combi Boiler Error Codes
      A light on your boiler will flash to indicate that there is a fault. Depending on the type of fault, the light will flash in a different sequence.
      There will be 4 quick flashes followed by a 5 second gap when the light is off and finally a series of longer flashes. The number of long flashes tells you which fault the boiler has.
      Fault Description System Behaviour
      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
      Worcester Bosch Greenstar Ri Boiler Error Codes
      Fault Description​ System Behaviour
      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
      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, however this is an issue that you could fix yourself if you feel confident enough, you can find out how in our handy guide.
      g_content_rows-repeater_items_title
    • Glow Worm
      Glow-worm Boiler Error Codes
      Boiler Model Fault Code Cause of Problem
      Betacom Red LED on Lockout – low water pressure (increase pressure to 1.5bar) and reset boiler
      Betacom Red LED flashing Overheat – check both overheat stats
      Betacom Yellow LED flashing Turn domestic hot water (DHW) control knob into temperature
      range and turn central heating (CH)
      temperature control knob into power (reset position) and wait for minimum of 30
      seconds before turning into either summer or temperature position
      Betacom Yellow LED on Flame present on the burner
      Betacom Green LED on Boiler ready for operation
      Betacom Green LED off No power to boiler – Check for 230volts into the appliance,
      check fuse on printed circuit board (PCB)
      Betacom / Ultracom₂ cxi / sxi / 35 F00 / F10 / F71 Flow heating temperature sensor fault
      Betacom / Ultracom₂ cxi / sxi / 35 F01 / F11 Return heating temperature sensor fault
      Betacom / Ultracom₂ cxi / sxi / 35 F20 Overheating fault
      Betacom / Ultracom₂ cxi / sxi / hxi / 35 / Flexicom cx / hx / sx F9 / F22 Low water pressure (or ignition temperature rise too slow)
      Betacom / Ultracom₂ cxi / sxi / 35 F26 / F77 Fault in gas valve
      Betacom / Ultracom₂ cxi / sxi / 35 / CI / hxi / Xtramax HE F27 / F16 Flame detection fault
      All Boilers F28 / F1 / F4 Ignition fault (flame detection)
      Betacom / Ultracom₂ cxi / sxi / 35 F29 Loss of flame during operation
      Betacom / Ultracom₂ cxi / sxi / 35 F32 Incorrect air pressure
      Betacom / Ultracom₂ cxi / sxi / 35 F49 EBUS voltage fault
      Betacom / Ultracom₂ cxi / sxi / 35 F61 / F62 / F63 / F64 / F65 / F67 Fault in the main board
      Betacom / Ultracom₂ cxi / sxi / 35 F68 Fluctuation of flame signal
      Betacom / Ultracom₂ cxi / sxi / 35 F70 User interface incompatible with the main board
      Betacom / Ultracom₂ cxi / sxi / 35 F72 / F84 Permanent temperature difference between flow and return heating sensors
      Betacom / Ultracom₂ cxi / sxi / 35 F73 / F74 Heating circuit pressure sensor fault
      Betacom / Ultracom₂ cxi / sxi / 35 F76 Thermal fuse fault
      Betacom / Ultracom₂ cxi / sxi / 35 F83 Thermal fuse fault
      Betacom / Ultracom₂ cxi / sxi / 35 F85 Flow and Return heating sensor fault
      Betacom / Ultracom₂ cxi / sxi / 35 F86 Underfloor heating contact fault
      All Boilers ERR / F12 / F18 User interface fault
      Betacom c Temperature 30 flashing Fault on central heating (CH) thermistor
      Betacom c Temperature 40 flashing Fault on DHW thermistor
      Betacom c Temperature 50 flashing Fault on outside sensor
      Betacom c Temperature 60 flashing Low system pressure
      Betacom c Temperature 70 flashing Fault on APS
      Betacom c Temperature 80 flashing Overheat open circuit
      Betacom c Temperature 90 flashing Flame or gas failure
      Compact e / s No DHW Check dhw microswitch / Check external controls, Please test for 230V on switch live contact
      Compact e / s No C/H Check dhw microswitch if dhw demand led is lit / Check external controls, Please test for 230V on switch live contact
      Compact e / s No C/H but boiler is firing Check diverter motor and cartridge / Check external controls, Please test for 230V on switch live contact
      Compact e / s Boiler locks out within 10 seconds Check pump proving switch, air pressure switch and overheat state / Check pump proving switch, air pressure switch and overheat stat
      Compact e / s Poor burner pressure Check burner pressure/ignition adjustment pots on PCB
      Ci Range (plus) / Si range F2 Fan/APS
      All Boilers F5 Overheat Fault
      All Boilers F6 Central heating flow thermistor
      All Boilers F7 Domestic hot water thermistor
      All Boilers F8 Tank thermistor fault
      sxi / si / ci (plus) range / Xtramax HE F9 Water pressure sensor fault (please contact GW technical department for
      further information)
      All boilers F10 Central return flow thermistor
      All boilers F11 Main board connection fault
      Ci (plus) / cxi / hxi / si / sxi range F12 Connection fault between main printed circuit board (PCB) and display PCB
      Ci (plus) / cxi / hxi / si / sxi range F13 Main PCB connection fault
      Ci (plus) / cxi / hxi / si / sxi range F14 Central heating flow temperature > 95 degrees
      Ci (plus) / cxi / si / sxi range F15 Gas valve stepper motor fault
      Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE F17 Power supply is less than 170v
      Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE F19 Central heating thermistor unplugged
      Ci (plus) / cxi / hxi / si / sxi range / Xtramax HE F20 Software incompatibility
      cxi / hxi / sxi range / Flexicom cx F24 Central heating return temperature > 90 degrees
      cxi / hxi / sxi / Xtrafast 96/120 / Xtrafast 96/120E1 F25 / F26 / F11 Poor circulation
      ci range F3 Air fault
      ci range F3 Air fault
      cxi / sxi / hxi range/ Xtramax HE F2 / F3 Fan
      cxi / sxi range / Flexicom cx / hx / sx /
      hxi / Ultracom cxi / cx / hxi / sxi / Ultrapower sxi
      F3 Fan unable to reach ignition speed
      Flexicom cx / hx / sx / hxi / Ultracom cxi / cx / hxi / sxi F9 Water pressure sensor fault, blocked flow filter or pump fault
      Flexicom cx / hx / sx F11 Flow and or return thermistor fault
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE F13 PCB memory or sensing fault
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE F14 Gas valve control defective
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi / Xtramax HE F15 E-bus voltage failure
      All boilers F25 / F23 Circulation fault
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi F43 Generic error
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi F70 Software incompatible
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi F73 Unable to see pump activate
      Flexicom cx / hx / sx / Ultracom cxi / cx / hxi / sxi F77 Condensate pump error (optional)
      hxi range F9 Earlier models only (please contact GW technical department for further
      information)
      hxi range F9 Earlier models only (please contact GW technical department for further
      information)
      Ultracom₂ 35 Store F02 / F12 Hot water temperature sensor fault
      Ultracom₂ 35 Store F03 / F13 / F79 Storage tank temperature sensor fault
      Ultracom₂ 35 Store F81 Overheating of hot water circuit
      All Ultracom No display or Er loose connection X51
      Xtramax HE Range F24 Cental heating return temperature > 90 degrees
      Xtramax HE Range F25 Maximum temperature rise slope
      Xtramax HE Range F26 Maximum delta temperature
      Xtrafast 96/120 Range F00 No fault/td>
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F00 No fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F02 Air flow fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F05 Overheating
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F06 Central heating thermistor/wiring fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F08 Storage vessel thermistor/wiring fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F09 System pressure sensor fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F10 Fan fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F13 Main printed circuit board (PCB) fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F14 Central heating flow temperature > 97 degrees
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F15 Gas mechanism fault
      Xtrafast 96/120 Range / Xtrafast 96/120E1 Range F20 Communication fault

      Glow-worm Energy Boiler Range Error Codes

      Fault Code Cause of Problem
      F.00 Flow temperature sensor
      F.00 Flow temperature sensor
      F.10 Flow temperature sensor short circuit
      F.11 Flow temperature sensor short circuit
      F.12 and F.91 Cylinder temperature sensor short circuit
      F.13 Domestic hot water cylinder temperature sensor short circuit
      F.20 Safety switch-off – overheating temperature reached
      F.22 Safety switch-off – low water pressure in the boiler
      F.23 Safety switch-off – temperature difference too great (NTC1/NTC2)
      F.24 Safety switch-off – temperature rise too fast
      F.25 Safety switch-off – flue gas temperature too high
      F.27 Safety switch-off – fault in flame detection
      F.28 Ignition unsuccessful when starting up
      F.29 Flame loss
      F.32 Fan frost protection function active – fan speed outside the tolerance values
      F.33 Fan frost protection function active – air pressure switch fault
      FA9 eBUS fault – voltage too low
      F.61 Gas valve control system fault
      F.82 Gas valve switch-off control fault
      F.83 EEPROM fault – electronics defective
      F.64 Electronics/sensor/analogue-to-digital converter fault
      F.85 Electronics temperature too high
      F.67 Value sent back by ASIC is incorrect (flame signal)
      F.88 Unstable flame (analogue input), underfloor heating contact or gas valve fault
      F.70 Invalid product code (DSN)
      F.71 Flow/return temperature sensor
      F.72 Deviation in the water pressure sensor/return temperature sensor
      F.73 Water pressure sensor not connected or has short-circuited
      F.74 Electrical problem in the water pressure sensor
      F.75 Pressure sensor fault
      F.78 The safety cut-out in the primary heat exchanger is defective
      F.77 Fault: Condensate or smoke
      F.78 Interruption to domestic hot water (DHW) outlet sensor at external controller
      F.83 Burner temperature sensor fault
      F.84 Flow/return temperature sensor fault
      F.85 Temperature sensor fault
      F.87 Electrodes fault
      F.89 Pump fault
      Connection No communication between the printed circuit board (PCB) and the user interface
      Glow-worm Error Codes F1, F4, F28 or F29
      If you are seeing the error codes F1, F4 F28 or F29 on your boiler there’s an issue with your condensate pipe.
      This error appears when your pipe is frozen, which can happen during the cold months as it runs outdoors.
      You can fix this issue yourself if you feel confident enough, otherwise call an engineer, by thawing out the
      pipe which you can find out how to do with our handy guide to thawing a condensate pipe.
      g_content_rows-repeater_items_title
    • Vaillant
      Vaillant Turbomax Plus 824/828E
      Fault Code Possible Cause Meaning
      F.00 NTC FAULTS This means that your Flow NTC (Negative Temperature Coefficient Thermostat)
      cable is either defective or broken and needs to be replaced
      F.01 NTC FAULTS (feed temperature sensor)
      – faulty connection and open circuit.
      This means that your Flow NTC (Negative Temperature Coefficient Thermostat)
      cable is either defective or broken and needs to be replaced
      F.10 NTC FAULTS (feed temperature sensor) – short circuit
      F.11
      F.13 NTC FAULTS (feed temperature sensor) – short circuit
      F.20 NTC FAULTS (feed temperature sensor) Your boiler has exceeded the maximum temperature
      and needs to be allowed to cool down
      F.22 DRY FIRE, LOW WATER IN SYSTEM/OVERHEAT This means that there’s either no water in your system,
      you have a defective pump or the pump lead is defective
      F.24 LOW WATER, OR PUMP FAILURE/BLOCKAGE Your pump could be obstructed, running at low capacity,
      or there could be air trapped in your appliance.
      Additionally, the pressure in your system might be too low.
      F.28 NO IGNITION/IGNITION PROBLEM This means there’s either insufficient gas in the system, a defective electrode,
      ignition lead or electronic ignitor
      F.29 FLAME EXTINGUISHED. FAN/FLUE PROBLEM/GAS Your flame, or pilot light has gone out. Check your flue duct or gas supply to
      see if there is a problem there.
      F.60 GAS VALVE CONTROL – DEFECTIVE Your cable loom which connects to your gas valve might have short circuited.
      Alternatively, you could have a defective gas valve assembly or electronic control system.
      F.61 GAS VALVE CONTROL – DEFECTIVE Your cable loom which connects to your gas valve may have short circuited.
      Alternatively, you could have a defective gas valve assembly or electronic control system.
      F.62 DEFECTIVE GAS VALVE CLOSURE MECHANISM Your boiler has exceeded the maximum temperature and needs to be allowed to cool down
      F.63 EEPROM (Electrically Erasable Programmable Read-Only Memory) ERROR This is an electronic fault within your system.
      F.64 ELECTRONIC SYSTEM/SENSOR FAULT Your flow or back flow NTC has suffered a short circuit, or an electronic fault
      F.65 ELECTRONIC SYSTEM TEMPERATURE TOO HIGH This can happen because of an external heat source or an electrical fault
      F.67 ELECTRONIC FAULT IN FLAME SYSTEM

      Vaillant EcoMax Pro 18/28E

      Fault Code​ Possible Cause
      F.1 Lack of gas, a fault with the ignition or flue or you may need to adjust the
      gas valve or replace a defective electrode lead.
      F.4 Ignition fault.
      F.5 The system has suffered a fault due to overheating.
      F.6 Your flow NTC has developed a fault.
      F.17 Check the polarity of your system.
      F.24 Pump-related faults – the pump could have failed, it may have over run or
      there could be an issue with the airlock
      Vaillant Ecomax Pro 828E
      Fault Code Possible Cause
      F.00, .04, .05, .10, .14, .15 All of these are NTC faults, and are best resolved by first changing all NTC
      to make diagnosis earlier.
      F.21 The pilot flame has failed.
      F.22 There is insufficient water in your system.
      F.11 A blockage in the appliance is preventing the system from flowing as it
      should.
      F.12 A blockage in the appliance is affecting the system’s pressure.
      F.13 The appliance is blocked because of a water deficiency.

      Vaillant EcoTEC 65kW Error Codes

      Fault Code Possible Cause
      S.O Heating issue, no heat demand
      S.1 Fan start-up error
      S.2 Pump flow error
      S.3 Heating mode error – ignition problem
      S.4 Heat mode – burner on error
      S.6 Heating mode – fan overrun error
      S.7 Heating mode – pump overrun error
      S.8 Heating remaining cut off for XX amount of time
      S.31 No heat demand summer operating mode
      S.34 Heating mode frost protection error
      S.20 Hot water requirement error
      S.22 Hot water handling pump flow error
      S.24 Hot water operation burner is on
      S.85 Service message quantity of circulation water

      Vaillant EcoTEC Pro / EcoTEC Plus Error Codes

      Fault Code Possible Cause
      F.00 / F.0 Flow temperature sensor interruption
      F.01 / F.1 Return temperature sensor interruption
      F.10 Flow NTC short circuit
      F.11 Return NTC short circuit
      F.20 Safety switch off temperature limiter
      F.22 Safety switch off low water pressure
      F.23 Safety switch off temperature difference too great
      F.24 Safety switch off temperature is rising to fast
      F.25 Safety switch off flue gas temperature too high
      F.26 Error with gas valve – possible no function
      F.27 Safety switch off flame simulation
      F.28 Failure during start up – ignition unsuccessful to start
      F.29 Failure during operation – re-ignition unsuccessful
      F.32 Fan error
      F.49 eBUS error – possible short circuit
      F.61 Error with gas valve regulation
      F.62 Error with gas valve – switch off delay
      F.63 EEPROM error
      F.64 Electronics / NTC error
      F.65 Electronic temperature error could be overheating due to external
      influences
      F.67 Electronics flame signal error
      F.68 Unstable flame signal error air in gas
      F.70 Invalid device specific number (DSN)
      F.71 Flow NTC error – flow temperature sensor signal constant value
      F.72 Flow return NTC error – temperature difference too great
      F.73 Water pressure sensor signal in the wrong range, it is too low
      F.74 Water pressure sensor signal outside correct range, the sensor signal is
      too high
      F.75 Error with pressure – no pressure change detection when starting the
      pump
      F.76 Overheating protection on – primary heat exchanger has responded
      F.77 Flue non return flap condensate pump error
      F.78 Interruption to DHW outlet sensor at external controller
      F.83 Flow and or return temperature sensor error
      F.84 Error with flow/return temperature sensor temperature changing error
      F.85 Error with flow and return temperature, sensor incorrectly fitted
      CONNECTION No communication with the PCB

      Vaillant EcoTEC Pro / EcoTEC Plus Error Codes

      Fault Code Possible Cause
      S.00 Heating mode error – no heat demand
      S.01 Heating mode fan start-up
      S.02 Heating mode error – water pump running
      S.03 Heating mode – ignition sequence error
      S.04 Heating mode – burner ignited
      S.06 Heating mode – fan overrun error
      S.07 Heating mode – pump overrun error
      S.08 Heating remaining cut off time xx minutes
      S.10 Hot water demand via impeller sensor
      S.11 DHW mode fan start up error
      S13 DHW mode ignition error
      S.14 Hot water demand via fan sensor error
      S.15 DHW mode pump and fan overrun
      S.16 DHW mode – fan overrun error
      S.17 DHW mode – pump overrun error
      S.20 DHW mode – burner on error
      S.21 DHW mode – fan start up error
      S.22 DHW demand – error pump running
      S.23 DHW ignition error
      S.24 DHW mode – burner error
      S.25 DHW mode – pump or fan overrun error
      S.26 DHW mode – fan overrun
      S.27 DHW mode – pump overrun
      S.28 Hot water burner anti-cycling time
      S.30 Room thermostat is blocking heating mode
      S.31 No heat demand boiler in summer operating mode
      S.32 Waiting period because of fan speed deviation
      S.34 Heating mode frost protection error
      S.39 Burner off contact has been triggered this could be because of contact
      thermostat or condensate pump
      S.40 Comfort safety mode active
      S.41 Water pressure > 2.8 bar
      S.42 Flue non return flap return signal blocks burner operation
      S.46 Comfort safety mode flame loss at minimum load
      S.53 Boiler is in waiting period of modulation f block function due to water
      shortage
      S.54 Boiler is in waiting period of operation, blocking function as a result
      S.57 Waiting period comfort safety mode
      S.58 Modulation limitation due to noise / wind error
      S.61 Gas family check unsuccessful

      Vaillant EcoTEC Plus Regular Gas Boiler Error Codes

      Fault Code Possible Cause
      S.20 Warnstar demand
      S.21 Fan running
      S.22 Pump running
      S.23 Ignition sequence
      S.24 Burner ignited
      S.25 Fan and water pump running
      S.26 Fan overrun
      S.27 Pump overrun
      S.28 Anti-cycling mode
      S.30 No heating demand from external controls
      S.31 Central heating thermostat knob turned off
      S.32 Heat exchanger antifreeze active as fan speed variation is too high
      S.34 Anti-frost mode is active
      S.36 Not heating demand form low voltage
      S.41 Water pressure greater than 2.9 bar
      S.42 Response from accessory module or defective condensate pump is
      blocking burner operation
      S.53 Appliance is within the waiting period of the block operation function due
      to water shortage
      S.54 Appliance is within the waiting period of the block operation due to water
      shortage
      S.96 Return sensor error
      S.98 Flow return sensor check is running demand is block
      D.0 Heating part load error
      D.1 Water pump overrun – time for heat mode
      D.2 Max burner anti-cycling period at 20c flow temperature
      D.3 Hot water flow temperature reading
      D.4 Current temperature for warm stat sensor
      D.7 Warm start temperature target value
      D.8 External controls heat demand
      D.9 Flow target temperature from external analogue regulator terminal
      D.10 Status internal heating pump error
      D,11 Status external heating pump error
      D.12 Cylinder charging pump via accessory module
      D.13 Hot water circulation pump
      D.22 Hot water demand
      D.23 Summer/Winter function
      D.25 Hot water activation via ebus control
      D.30 Control signal for both gas valves
      D.33 Fan speed target value
      D.34 Fan speed actual value
      D.36 Hot water flow sensor
      D.40 Flow temperature target value
      D.41 Return temperature actual value
      D.44 Digitised ionisation potential error
      D.47 Outside temperature with weather compensator – Vaillant controller only
      D.76 Remaining burner anti-cycling time in min
      D.90 Digital regulator status
      D.91 DCF status with connected external probe
      D.97 Activation of the second diagnostic level
      D.17 Heating glow return regulation
      D.18 Pump mode return
      D.19 Operating modes of the two speed heating pump
      D.20 Maximum set value for target cylinder
      D.27 Switching accessory relay 1
      D.28 Switching accessory relay 2
      D.50 Offset for minimum speed
      D.51 Offset for maximum speed
      D.58 Activation of solar reheating
      D.60 Number of safety temperature cut off
      D.61 Number of unsuccessful lockouts
      D.64 Average ignition times
      D.65 Maximum ignition t