Glow-worm
Glow-worm Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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F1
Boiler locks out and displays F1, burner does not ignite
Ignition Failure / Flame Not Detected
F10
Boiler shows F10, will not start, temperature reading may be abnormal
Flow Temperature Sensor Fault (NTC Open/Short)
F11
Boiler displays F11, may run briefly then shut down, flow temperature reading erratic
Return Temperature Sensor Fault (NTC Open/Short)
F12
Boiler shows F12, may not respond to controls, display may be frozen
Communication Fault Between User Interface and Main PCB
F13
Boiler displays F13, may not respond to room thermostat or external controls
External Control / eBUS Communication Fault
F14
Boiler shows F14, no heating or hot water, may occur after power surge
PCB Internal Fault / Configuration Error
F15
Boiler displays F15, may run pump but not fire burner
Gas Valve Control Fault
F16
Boiler shows F16, burner may light then shut down, combustion unstable
Flame Signal Too Weak / Ionisation Fault
F20
Boiler displays F20 and shuts down, casing may feel very hot
Overheat Thermostat Trip / Primary Overheat
F22
Boiler shows F22, no heating or hot water, pressure gauge low or at zero
Low Water Pressure / Dry Fire Protection
F23
Boiler displays F23, may cycle on and off rapidly, poor heating performance
Flow/Return Temperature Differential Too High
F24
Boiler shows F24, rapid temperature rise then shutdown
Low Water Content / Pump or Flow Fault
F25
Boiler displays F25, burner shuts down, may be associated with flue issues
Flue Gas Temperature Too High / Flue Sensor Trip
F26
Boiler shows F26, burner does not light, fan may run
Gas Valve Regulation Fault
F27
Boiler displays F27, ignition aborted, may occur with incorrect gas type or contamination
Flame Detection Error / False Flame Signal
F28
Boiler shows F28, ignition fails, no flame established
Ignition Failure (No Flame Detected)
F29
Boiler displays F29, flame goes out during operation, intermittent hot water or heating
Flame Loss During Operation
F3
Boiler shows F3 and shuts down, no heating or hot water
Fan Fault / Fan Not Running or Feedback Error
F32
Boiler shows F32, fan speed error, may not ignite
Fan Speed / Hall Sensor Fault
F36
Boiler displays F36, flue gas recirculation or blockage detected
Flue Gas Recirculation / Blocked Flue
F4
Boiler displays F4 and will not fire, intermittent ignition then lockout
Ignition Lockout / Flame Establishment Failure
F5
Boiler shows F5 and shuts down, fan may run briefly then stop
Air Pressure Switch / Flue System Fault
F61
Boiler shows F61, gas valve error, no ignition
Gas Valve Electrical Fault
F62
Boiler displays F62, gas valve closing delay or sticking
Gas Valve Closure Fault
F63
Boiler shows F63, internal error, may not respond to controls
EEPROM / PCB Configuration Fault
F64
Boiler displays F64, sensor or PCB temperature input error
NTC Sensor / PCB Analogue Fault
F67
Boiler shows F67, flame detection error, may not ignite
PCB Flame Detection Circuit Fault
F9
Boiler displays F9 and locks out, no heating or hot water
Flame Detection Fault / Flame Signal Lost
Symptom
Boiler display is on but does not respond to room thermostat or programmer
Control Signal Not Reaching Boiler
Symptom
Boiler emits a burning smell or visible smoke from casing
Overheating Electrical Component or Debris on Heat Exchanger
Symptom
Boiler fires for hot water but not for central heating
Heating Demand / Diverter or Control Fault
Symptom
Boiler flue terminal dripping water externally
Condensate Discharge from Flue
Symptom
Boiler frequently needs manual reset but no clear error code is shown
Intermittent Lockout / Unstable Operation
Symptom
Boiler frequently short cycles (turns on and off rapidly) during heating
Short Cycling / Oversized Boiler or Poor Control
Symptom
Boiler is very noisy during operation (whining, grinding, or rattling)
Mechanical Noise from Fan, Pump, or Combustion
Symptom
Boiler leaking water from underneath the casing
Internal Water Leak
Symptom
Boiler losing pressure daily, user must keep topping up via filling loop
Chronic System Pressure Loss
Symptom
Boiler making loud banging or kettling noises when heating is on
Kettling / Localised Boiling in Heat Exchanger
Symptom
Boiler provides heating but no domestic hot water on a combi model
DHW Priority / Diverter Valve or Sensor Fault
Symptom
Boiler runs but radiators do not get hot or only partially warm
Poor Central Heating Circulation
Symptom
Boiler will not start at all, no display or lights
No Power / Electrical Supply Fault
Symptom
Condensate pipe repeatedly freezing in cold weather, boiler stops working
Frozen Condensate Discharge
Symptom
Hot water temperature fluctuates or runs hot then cold on a combi boiler
Unstable Domestic Hot Water Temperature
Symptom
Radiators upstairs get hot but downstairs remain cold
Partial Circulation / Balancing or Sludge Issue
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| F1 |
Boiler locks out and displays F1, burner does not ignite
|
Ignition Failure / Flame Not Detected | View Details |
| F10 |
Boiler shows F10, will not start, temperature reading may be abnormal
|
Flow Temperature Sensor Fault (NTC Open/Short) | View Details |
| F11 |
Boiler displays F11, may run briefly then shut down, flow temperature reading erratic
|
Return Temperature Sensor Fault (NTC Open/Short) | View Details |
| F12 |
Boiler shows F12, may not respond to controls, display may be frozen
|
Communication Fault Between User Interface and Main PCB | View Details |
| F13 |
Boiler displays F13, may not respond to room thermostat or external controls
|
External Control / eBUS Communication Fault | View Details |
| F14 |
Boiler shows F14, no heating or hot water, may occur after power surge
|
PCB Internal Fault / Configuration Error | View Details |
| F15 |
Boiler displays F15, may run pump but not fire burner
|
Gas Valve Control Fault | View Details |
| F16 |
Boiler shows F16, burner may light then shut down, combustion unstable
|
Flame Signal Too Weak / Ionisation Fault | View Details |
| F20 |
Boiler displays F20 and shuts down, casing may feel very hot
|
Overheat Thermostat Trip / Primary Overheat | View Details |
| F22 |
Boiler shows F22, no heating or hot water, pressure gauge low or at zero
|
Low Water Pressure / Dry Fire Protection | View Details |
| F23 |
Boiler displays F23, may cycle on and off rapidly, poor heating performance
|
Flow/Return Temperature Differential Too High | View Details |
| F24 |
Boiler shows F24, rapid temperature rise then shutdown
|
Low Water Content / Pump or Flow Fault | View Details |
| F25 |
Boiler displays F25, burner shuts down, may be associated with flue issues
|
Flue Gas Temperature Too High / Flue Sensor Trip | View Details |
| F26 |
Boiler shows F26, burner does not light, fan may run
|
Gas Valve Regulation Fault | View Details |
| F27 |
Boiler displays F27, ignition aborted, may occur with incorrect gas type or contamination
|
Flame Detection Error / False Flame Signal | View Details |
| F28 |
Boiler shows F28, ignition fails, no flame established
|
Ignition Failure (No Flame Detected) | View Details |
| F29 |
Boiler displays F29, flame goes out during operation, intermittent hot water or heating
|
Flame Loss During Operation | View Details |
| F3 |
Boiler shows F3 and shuts down, no heating or hot water
|
Fan Fault / Fan Not Running or Feedback Error | View Details |
| F32 |
Boiler shows F32, fan speed error, may not ignite
|
Fan Speed / Hall Sensor Fault | View Details |
| F36 |
Boiler displays F36, flue gas recirculation or blockage detected
|
Flue Gas Recirculation / Blocked Flue | View Details |
| F4 |
Boiler displays F4 and will not fire, intermittent ignition then lockout
|
Ignition Lockout / Flame Establishment Failure | View Details |
| F5 |
Boiler shows F5 and shuts down, fan may run briefly then stop
|
Air Pressure Switch / Flue System Fault | View Details |
| F61 |
Boiler shows F61, gas valve error, no ignition
|
Gas Valve Electrical Fault | View Details |
| F62 |
Boiler displays F62, gas valve closing delay or sticking
|
Gas Valve Closure Fault | View Details |
| F63 |
Boiler shows F63, internal error, may not respond to controls
|
EEPROM / PCB Configuration Fault | View Details |
| F64 |
Boiler displays F64, sensor or PCB temperature input error
|
NTC Sensor / PCB Analogue Fault | View Details |
| F67 |
Boiler shows F67, flame detection error, may not ignite
|
PCB Flame Detection Circuit Fault | View Details |
| F9 |
Boiler displays F9 and locks out, no heating or hot water
|
Flame Detection Fault / Flame Signal Lost | View Details |
| – |
Boiler display is on but does not respond to room thermostat or programmer
|
Control Signal Not Reaching Boiler | View Details |
| – |
Boiler emits a burning smell or visible smoke from casing
|
Overheating Electrical Component or Debris on Heat Exchanger | View Details |
| – |
Boiler fires for hot water but not for central heating
|
Heating Demand / Diverter or Control Fault | View Details |
| – |
Boiler flue terminal dripping water externally
|
Condensate Discharge from Flue | View Details |
| – |
Boiler frequently needs manual reset but no clear error code is shown
|
Intermittent Lockout / Unstable Operation | View Details |
| – |
Boiler frequently short cycles (turns on and off rapidly) during heating
|
Short Cycling / Oversized Boiler or Poor Control | View Details |
| – |
Boiler is very noisy during operation (whining, grinding, or rattling)
|
Mechanical Noise from Fan, Pump, or Combustion | View Details |
| – |
Boiler leaking water from underneath the casing
|
Internal Water Leak | View Details |
| – |
Boiler losing pressure daily, user must keep topping up via filling loop
|
Chronic System Pressure Loss | View Details |
| – |
Boiler making loud banging or kettling noises when heating is on
|
Kettling / Localised Boiling in Heat Exchanger | View Details |
| – |
Boiler provides heating but no domestic hot water on a combi model
|
DHW Priority / Diverter Valve or Sensor Fault | View Details |
| – |
Boiler runs but radiators do not get hot or only partially warm
|
Poor Central Heating Circulation | View Details |
| – |
Boiler will not start at all, no display or lights
|
No Power / Electrical Supply Fault | View Details |
| – |
Condensate pipe repeatedly freezing in cold weather, boiler stops working
|
Frozen Condensate Discharge | View Details |
| – |
Hot water temperature fluctuates or runs hot then cold on a combi boiler
|
Unstable Domestic Hot Water Temperature | View Details |
| – |
Radiators upstairs get hot but downstairs remain cold
|
Partial Circulation / Balancing or Sludge Issue | View Details |
No matching codes found
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