Worcester Bosch
Worcester Bosch Boilers Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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A1
Boiler shows A1 and stops, often with gurgling noises, especially in cold weather.
Blocked or Frozen Condensate Pipe
A7
Boiler displays A7, hot water temperature is erratic or incorrect.
Hot Water Temperature Sensor Fault (DHW NTC)
A8
Boiler shows A8, hot water may not reach set temperature or may fluctuate.
DHW Flow Sensor / Turbine Fault
A9
Boiler displays A9, often with poor or no hot water delivery.
DHW Sensor / Flow Recognition Fault
C1 264
Boiler shows C1 264, often related to low water pressure or circulation issues.
Low Water Content / Circulation Fault
C1 286
Boiler intermittently shows C1 286, often during heating demand.
Pump Speed / Circulation Fault
C6
Boiler shows C6, fan speed or air pressure issues detected.
Fan Speed / Air Pressure Switch Fault
C7
Boiler displays C7, fan not detected or not running.
Fan Not Running / Fan Feedback Fault
CE 207
Boiler shows CE 207, communication error between user interface and main PCB.
Control PCB / Display Communication Fault
CE 208
Boiler displays CE 208, often with unresponsive controls.
User Interface / Control Panel Fault
E1 218
Boiler displays E1 218, fan runs but ignition does not proceed correctly.
Air Pressure Switch / Fan Proving Fault
E1 224
Boiler shows E1 224, ignition sequence stops quickly, no sustained flame.
Flame Loss During Operation
E1 227
Boiler displays E1 227, attempts to ignite but fails, then locks out.
No Flame Signal After Ignition Attempt
E1 332
Boiler shows E1 332, may run briefly then shut down, often associated with sensor issues.
Flow Temperature Sensor Fault / NTC Error
E1 338
Boiler displays E1 338, often intermittent, affecting temperature readings.
Return Temperature Sensor Fault / NTC Error
E2
Boiler shows E2 and shuts down, often linked to overheat or sensor issues on some Worcester Bosch models.
Overheat Thermostat / Safety Temperature Limiter Fault
E5
Boiler displays E5, often associated with fan or air pressure issues on certain Worcester Bosch boilers.
Fan / Airflow Fault
E6
Boiler shows E6, often related to flow temperature sensor or overheat on some Worcester Bosch models.
Flow Temperature Sensor / Overheat Fault
E9
Boiler shows E9 and shuts down, may overheat quickly or make kettling noises before lockout.
Primary Heat Exchanger Overheat / Safety Temperature Limiter Trip
E9 224
Boiler intermittently locks out with E9 224, often during high demand.
Intermittent Overheat / Flame Loss Combination Fault
EA
Boiler locks out and displays EA, no ignition, red fault light on, burner does not light.
Ignition Failure / Flame Not Detected
H07
Boiler shows H07, often related to low system pressure on some Worcester Bosch models.
Low System Pressure Warning
H11
Boiler displays H11, often associated with flow sensor or pump issues.
Insufficient Flow / Flow Switch Fault
H13
Boiler shows H13, often linked to sensor calibration or temperature differential issues.
Temperature Differential / Sensor Calibration Fault
H17
Boiler displays H17, often related to flue gas temperature or sensor issues.
Flue Gas Temperature / Sensor Fault
H19
Boiler shows H19, often associated with condensate or siphon issues.
Condensate Siphon / Drainage Fault
U6
Boiler shows U6, often related to flame detection or gas valve control.
Flame Detection / Gas Valve Control Fault
U9
Boiler displays U9, often indicating a coding plug or configuration issue.
Coding Plug / Configuration Fault
Symptom
Boiler does not respond to room thermostat or programmer, stays off even when heat is requested.
External Controls / Communication Fault
Symptom
Boiler frequently cycles on and off, radiators get hot then cool quickly, room never reaches set temperature.
Short Cycling / Control or Sizing Issue
Symptom
Boiler is very noisy with whirring, grinding, or rattling sounds during operation.
Mechanical Noise from Fan or Pump
Symptom
Boiler leaks water from underneath the casing.
Internal Water Leak
Symptom
Boiler locks out intermittently, especially in very cold weather, with gurgling sounds in the boiler.
Frozen or Partially Blocked Condensate Pipe
Symptom
Boiler makes loud banging, knocking, or kettling noises when heating or producing hot water.
Kettling / Localised Boiling in Heat Exchanger
Symptom
Boiler or flue emits unusual smells (metallic, burning, or exhaust-like) during operation.
Combustion / Flue Gas Leakage Risk
Symptom
Boiler pressure keeps dropping to zero over hours or days, requiring frequent top-ups.
System Water Loss / Pressure Loss
Symptom
Boiler pressure rises rapidly when heating is on and may discharge water from the pressure relief pipe.
Failed Expansion Vessel / Over-Pressurisation
Symptom
Boiler provides hot water but radiators only get warm at the bottom or some radiators stay cold.
Poor Circulation / Sludged System
Symptom
Boiler runs but radiators do not get hot, hot water works normally.
Central Heating Flow Fault / Diverter Valve Stuck on Hot Water
Symptom
Boiler runs but some radiators are hot and others remain cold, even after bleeding.
System Imbalance / Blocked Radiator or Pipe
Symptom
Boiler will not start at all, no lights or display, completely dead.
No Power to Boiler
Symptom
Hot water temperature fluctuates, running hot then cold, especially at low flow rates.
Inconsistent DHW Temperature Control
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| A1 |
Boiler shows A1 and stops, often with gurgling noises, especially in cold weather.
|
Blocked or Frozen Condensate Pipe | View Details |
| A7 |
Boiler displays A7, hot water temperature is erratic or incorrect.
|
Hot Water Temperature Sensor Fault (DHW NTC) | View Details |
| A8 |
Boiler shows A8, hot water may not reach set temperature or may fluctuate.
|
DHW Flow Sensor / Turbine Fault | View Details |
| A9 |
Boiler displays A9, often with poor or no hot water delivery.
|
DHW Sensor / Flow Recognition Fault | View Details |
| C1 264 |
Boiler shows C1 264, often related to low water pressure or circulation issues.
|
Low Water Content / Circulation Fault | View Details |
| C1 286 |
Boiler intermittently shows C1 286, often during heating demand.
|
Pump Speed / Circulation Fault | View Details |
| C6 |
Boiler shows C6, fan speed or air pressure issues detected.
|
Fan Speed / Air Pressure Switch Fault | View Details |
| C7 |
Boiler displays C7, fan not detected or not running.
|
Fan Not Running / Fan Feedback Fault | View Details |
| CE 207 |
Boiler shows CE 207, communication error between user interface and main PCB.
|
Control PCB / Display Communication Fault | View Details |
| CE 208 |
Boiler displays CE 208, often with unresponsive controls.
|
User Interface / Control Panel Fault | View Details |
| E1 218 |
Boiler displays E1 218, fan runs but ignition does not proceed correctly.
|
Air Pressure Switch / Fan Proving Fault | View Details |
| E1 224 |
Boiler shows E1 224, ignition sequence stops quickly, no sustained flame.
|
Flame Loss During Operation | View Details |
| E1 227 |
Boiler displays E1 227, attempts to ignite but fails, then locks out.
|
No Flame Signal After Ignition Attempt | View Details |
| E1 332 |
Boiler shows E1 332, may run briefly then shut down, often associated with sensor issues.
|
Flow Temperature Sensor Fault / NTC Error | View Details |
| E1 338 |
Boiler displays E1 338, often intermittent, affecting temperature readings.
|
Return Temperature Sensor Fault / NTC Error | View Details |
| E2 |
Boiler shows E2 and shuts down, often linked to overheat or sensor issues on some Worcester Bosch models.
|
Overheat Thermostat / Safety Temperature Limiter Fault | View Details |
| E5 |
Boiler displays E5, often associated with fan or air pressure issues on certain Worcester Bosch boilers.
|
Fan / Airflow Fault | View Details |
| E6 |
Boiler shows E6, often related to flow temperature sensor or overheat on some Worcester Bosch models.
|
Flow Temperature Sensor / Overheat Fault | View Details |
| E9 |
Boiler shows E9 and shuts down, may overheat quickly or make kettling noises before lockout.
|
Primary Heat Exchanger Overheat / Safety Temperature Limiter Trip | View Details |
| E9 224 |
Boiler intermittently locks out with E9 224, often during high demand.
|
Intermittent Overheat / Flame Loss Combination Fault | View Details |
| EA |
Boiler locks out and displays EA, no ignition, red fault light on, burner does not light.
|
Ignition Failure / Flame Not Detected | View Details |
| H07 |
Boiler shows H07, often related to low system pressure on some Worcester Bosch models.
|
Low System Pressure Warning | View Details |
| H11 |
Boiler displays H11, often associated with flow sensor or pump issues.
|
Insufficient Flow / Flow Switch Fault | View Details |
| H13 |
Boiler shows H13, often linked to sensor calibration or temperature differential issues.
|
Temperature Differential / Sensor Calibration Fault | View Details |
| H17 |
Boiler displays H17, often related to flue gas temperature or sensor issues.
|
Flue Gas Temperature / Sensor Fault | View Details |
| H19 |
Boiler shows H19, often associated with condensate or siphon issues.
|
Condensate Siphon / Drainage Fault | View Details |
| U6 |
Boiler shows U6, often related to flame detection or gas valve control.
|
Flame Detection / Gas Valve Control Fault | View Details |
| U9 |
Boiler displays U9, often indicating a coding plug or configuration issue.
|
Coding Plug / Configuration Fault | View Details |
| – |
Boiler does not respond to room thermostat or programmer, stays off even when heat is requested.
|
External Controls / Communication Fault | View Details |
| – |
Boiler frequently cycles on and off, radiators get hot then cool quickly, room never reaches set temperature.
|
Short Cycling / Control or Sizing Issue | View Details |
| – |
Boiler is very noisy with whirring, grinding, or rattling sounds during operation.
|
Mechanical Noise from Fan or Pump | View Details |
| – |
Boiler leaks water from underneath the casing.
|
Internal Water Leak | View Details |
| – |
Boiler locks out intermittently, especially in very cold weather, with gurgling sounds in the boiler.
|
Frozen or Partially Blocked Condensate Pipe | View Details |
| – |
Boiler makes loud banging, knocking, or kettling noises when heating or producing hot water.
|
Kettling / Localised Boiling in Heat Exchanger | View Details |
| – |
Boiler or flue emits unusual smells (metallic, burning, or exhaust-like) during operation.
|
Combustion / Flue Gas Leakage Risk | View Details |
| – |
Boiler pressure keeps dropping to zero over hours or days, requiring frequent top-ups.
|
System Water Loss / Pressure Loss | View Details |
| – |
Boiler pressure rises rapidly when heating is on and may discharge water from the pressure relief pipe.
|
Failed Expansion Vessel / Over-Pressurisation | View Details |
| – |
Boiler provides hot water but radiators only get warm at the bottom or some radiators stay cold.
|
Poor Circulation / Sludged System | View Details |
| – |
Boiler runs but radiators do not get hot, hot water works normally.
|
Central Heating Flow Fault / Diverter Valve Stuck on Hot Water | View Details |
| – |
Boiler runs but some radiators are hot and others remain cold, even after bleeding.
|
System Imbalance / Blocked Radiator or Pipe | View Details |
| – |
Boiler will not start at all, no lights or display, completely dead.
|
No Power to Boiler | View Details |
| – |
Hot water temperature fluctuates, running hot then cold, especially at low flow rates.
|
Inconsistent DHW Temperature Control | View Details |
No matching codes found
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