Worcester Bosch
Worcester Bosch Furnaces 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 associated with low or no water pressure.
Low System Water Pressure
A2
Boiler displays A2 and will not run, often after overheating events.
Overheat Thermostat Tripped
A3
Boiler shows A3, often with the fan not running or running erratically.
Fan Fault / Air Proving Failure
A4
Boiler displays A4 and will not fire, often related to flue gas or air pressure sensing.
Air Pressure Switch / Flue Gas Sensor Fault
C6
Boiler shows C6, often with noisy fan operation or failure to ignite.
Fan Speed / Fan Running Too Slowly
C7
Boiler displays C7 and will not start, often indicating no fan feedback.
Fan Not Running / No Fan Feedback Signal
D1
Boiler shows D1 and may continue to run at reduced performance.
Sensor Calibration / Communication Error
D5
Boiler displays D5, often related to diverter valve or motorised valve issues.
Diverter Valve Positioning Fault
E1 218
Boiler shows E1 218 and will not ignite, often after power interruptions.
Ignition Lockout / No Flame Signal
E1 224
Boiler displays E1 224, often immediately after start-up, with no sustained flame.
Flame Detection Error at Start-Up
E1 227
Boiler shows E1 227 (or 227) and locks out, indicating flame loss during operation.
Flame Loss During Operation
E1 253
Boiler intermittently locks out with E1 253, often during windy conditions.
Flame Stability / Combustion Disturbance
E1 254
Boiler shows E1 254 and locks out, often after several failed ignition attempts.
Lockout Due to Repeated Ignition Failure
E1 256
Boiler displays E1 256, often with no response to thermostat calls.
External Control / Thermostat Fault
E1 260
Boiler shows E1 260, often with erratic temperature readings.
Flow Sensor / Turbine Fault (on combi models)
E1 332
Boiler shows E1 332, often associated with communication issues with external controls.
Bus Communication Error (e.g., with Worcester Bosch Wave or EasyControl)
E1 338
Boiler displays E1 338, often after power surges or wiring changes.
Internal PCB Fault / Configuration Error
E1 361
Boiler shows E1 361, often with erratic display behaviour.
User Interface / Display Communication Fault
E2
Boiler displays E2 and shuts down, often with no heating or hot water.
Flow Temperature Sensor (NTC) Fault
E3
Boiler shows E3 and stops, usually related to return temperature sensing.
Return Temperature Sensor (NTC) Fault
E5
Boiler displays E5, often with no heating or hot water and pump not running.
Pump Fault / No Water Circulation
E6
Boiler shows E6 and may cycle on and off rapidly, with incorrect temperature readings.
Domestic Hot Water (DHW) NTC Sensor Fault
E9
Boiler displays E9 and shuts down, often accompanied by rapid temperature rise or banging noises before lockout.
Overheat / Primary Circuit Over-Temperature
E9 219
Boiler intermittently locks out with E9 219, often during high demand.
Flow/Return Temperature Differential Too High
E9 224
Boiler intermittently locks out with E9 224, often after running for some time.
Intermittent Overheat / Sensor Discrepancy
EA
Boiler locks out with EA on display, no flame established, burner does not ignite.
Ignition Failure / Flame Not Detected
Symptom
Boiler cycles on and off rapidly without reaching set temperature.
Short Cycling
Symptom
Boiler frequently loses pressure and needs topping up every few days.
Chronic Pressure Loss
Symptom
Boiler is completely dead: no lights on display, no response to controls.
No Power / Electrical Supply Failure
Symptom
Boiler makes loud banging or kettling noises when heating is on.
Kettling / Localised Boiling in Heat Exchanger
Symptom
Boiler or flue emits unusual smells, such as burning, metallic, or exhaust-like odours.
Combustion / Overheating / Electrical Smell Issue
Symptom
Boiler runs but makes a high-pitched whine or screeching noise.
Mechanical Noise from Fan or Pump
Symptom
Boiler runs but radiators do not heat up or only get lukewarm.
Poor Central Heating Performance / Circulation Issue
Symptom
Boiler starts then shuts down after a few seconds without showing a specific error code.
Early Flame Failure / Safety Shutdown
Symptom
Condensate pipe dripping heavily or backing up, boiler may gurgle or cut out.
Condensate Drain Blockage / Siphon Issue
Symptom
Hot water temperature fluctuates or runs hot then cold during use.
Inconsistent Domestic Hot Water Temperature
Symptom
Radiators upstairs get hot but downstairs remain cold.
Partial Circulation / System Balancing Issue
Symptom
Water leaking from the bottom of the boiler casing.
Internal Water Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| A1 |
Boiler shows A1 and stops, often associated with low or no water pressure.
|
Low System Water Pressure | View Details |
| A2 |
Boiler displays A2 and will not run, often after overheating events.
|
Overheat Thermostat Tripped | View Details |
| A3 |
Boiler shows A3, often with the fan not running or running erratically.
|
Fan Fault / Air Proving Failure | View Details |
| A4 |
Boiler displays A4 and will not fire, often related to flue gas or air pressure sensing.
|
Air Pressure Switch / Flue Gas Sensor Fault | View Details |
| C6 |
Boiler shows C6, often with noisy fan operation or failure to ignite.
|
Fan Speed / Fan Running Too Slowly | View Details |
| C7 |
Boiler displays C7 and will not start, often indicating no fan feedback.
|
Fan Not Running / No Fan Feedback Signal | View Details |
| D1 |
Boiler shows D1 and may continue to run at reduced performance.
|
Sensor Calibration / Communication Error | View Details |
| D5 |
Boiler displays D5, often related to diverter valve or motorised valve issues.
|
Diverter Valve Positioning Fault | View Details |
| E1 218 |
Boiler shows E1 218 and will not ignite, often after power interruptions.
|
Ignition Lockout / No Flame Signal | View Details |
| E1 224 |
Boiler displays E1 224, often immediately after start-up, with no sustained flame.
|
Flame Detection Error at Start-Up | View Details |
| E1 227 |
Boiler shows E1 227 (or 227) and locks out, indicating flame loss during operation.
|
Flame Loss During Operation | View Details |
| E1 253 |
Boiler intermittently locks out with E1 253, often during windy conditions.
|
Flame Stability / Combustion Disturbance | View Details |
| E1 254 |
Boiler shows E1 254 and locks out, often after several failed ignition attempts.
|
Lockout Due to Repeated Ignition Failure | View Details |
| E1 256 |
Boiler displays E1 256, often with no response to thermostat calls.
|
External Control / Thermostat Fault | View Details |
| E1 260 |
Boiler shows E1 260, often with erratic temperature readings.
|
Flow Sensor / Turbine Fault (on combi models) | View Details |
| E1 332 |
Boiler shows E1 332, often associated with communication issues with external controls.
|
Bus Communication Error (e.g., with Worcester Bosch Wave or EasyControl) | View Details |
| E1 338 |
Boiler displays E1 338, often after power surges or wiring changes.
|
Internal PCB Fault / Configuration Error | View Details |
| E1 361 |
Boiler shows E1 361, often with erratic display behaviour.
|
User Interface / Display Communication Fault | View Details |
| E2 |
Boiler displays E2 and shuts down, often with no heating or hot water.
|
Flow Temperature Sensor (NTC) Fault | View Details |
| E3 |
Boiler shows E3 and stops, usually related to return temperature sensing.
|
Return Temperature Sensor (NTC) Fault | View Details |
| E5 |
Boiler displays E5, often with no heating or hot water and pump not running.
|
Pump Fault / No Water Circulation | View Details |
| E6 |
Boiler shows E6 and may cycle on and off rapidly, with incorrect temperature readings.
|
Domestic Hot Water (DHW) NTC Sensor Fault | View Details |
| E9 |
Boiler displays E9 and shuts down, often accompanied by rapid temperature rise or banging noises before lockout.
|
Overheat / Primary Circuit Over-Temperature | View Details |
| E9 219 |
Boiler intermittently locks out with E9 219, often during high demand.
|
Flow/Return Temperature Differential Too High | View Details |
| E9 224 |
Boiler intermittently locks out with E9 224, often after running for some time.
|
Intermittent Overheat / Sensor Discrepancy | View Details |
| EA |
Boiler locks out with EA on display, no flame established, burner does not ignite.
|
Ignition Failure / Flame Not Detected | View Details |
| – |
Boiler cycles on and off rapidly without reaching set temperature.
|
Short Cycling | View Details |
| – |
Boiler frequently loses pressure and needs topping up every few days.
|
Chronic Pressure Loss | View Details |
| – |
Boiler is completely dead: no lights on display, no response to controls.
|
No Power / Electrical Supply Failure | View Details |
| – |
Boiler makes loud banging or kettling noises when heating is on.
|
Kettling / Localised Boiling in Heat Exchanger | View Details |
| – |
Boiler or flue emits unusual smells, such as burning, metallic, or exhaust-like odours.
|
Combustion / Overheating / Electrical Smell Issue | View Details |
| – |
Boiler runs but makes a high-pitched whine or screeching noise.
|
Mechanical Noise from Fan or Pump | View Details |
| – |
Boiler runs but radiators do not heat up or only get lukewarm.
|
Poor Central Heating Performance / Circulation Issue | View Details |
| – |
Boiler starts then shuts down after a few seconds without showing a specific error code.
|
Early Flame Failure / Safety Shutdown | View Details |
| – |
Condensate pipe dripping heavily or backing up, boiler may gurgle or cut out.
|
Condensate Drain Blockage / Siphon Issue | View Details |
| – |
Hot water temperature fluctuates or runs hot then cold during use.
|
Inconsistent Domestic Hot Water Temperature | View Details |
| – |
Radiators upstairs get hot but downstairs remain cold.
|
Partial Circulation / System Balancing Issue | View Details |
| – |
Water leaking from the bottom of the boiler casing.
|
Internal Water Leak | View Details |
No matching codes found
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