Should a fault develop with your Worcester Bosch boiler, it will enter a safety lock-out mode, and fault code information will be generated as described below.
Worcester Bosch errors
Locking error
The boiler display will flash a warning triangle and fault code. At the same time a (static) cause code will also be displayed. Manual intervention (Pressing the reset button on the boiler fascia) is required following clearance of the fault.
Blocking error
The boiler will stop operating with no fault data displayed. The cause code, in the info menu, is accessed by pressing the spanner/return button. The condition will clear automatically when the associated fault clears e.g. waiting for an area to cool. In some cases a blocking error has a defined time duration prior to changing to a locking condition.
Fault error
Alpha numeric code indicating the fault group.
Cause error
Three digit number. During a blocking error (or normal operating status) it is not displayed, but accessed in the info menu via the spanner/return button. During a locking error the cause code flashes on the display.
Maintenance codes
These are displayed with the letter H followed by a number. The code advises of a situation that will need some attention but is not a fault that will stop the boiler from functioning. Some of the common ones are listed:
H11
Hot water outlet sensor defect, hot water can still be delivered but with less control.
H13
A time has been set in the Service interval function i.e. 1 to 72 months and that time has expired. Menu 2.5F allows this feature to be set (1 to 72), a 0 will disable this function.
Worcester Bosch fault codes: locking errors
9A: HCM (Heat control module)
- Cause code: 362
- Reset type: Reset button
- Possible cause: Incorrect HCM fitted
9U: HCM (Heat control module)
- Cause code: 233
- Reset type: Reset button
- Possible cause: Problem with the code plug (faulty or not connected)
B7: Internal error
- Cause code: 257
- Possible cause: Replace control board
C6: Fan problem
- Cause code: 215
- Reset type: Reset button
- Possible cause: Running too fast
C6: Fan problem
- Cause code: 216
- Reset type: Reset button
- Possible cause: Running too slow
C7: Fan problem
- Cause code: 214
- Reset type: Reset button
- Possible cause: Fan not running
C7: No airflow after a defined period of time
- Cause code: 217
- Reset type: Reset button
- Possible cause: Fan not running or airflow blocked
D1: Return sensor error
- Cause code: 240
- Reset type: Reset button
- Possible cause: Sensor wet or damaged (the boiler will block for 300 seconds before this condition)
D1: Return sensor error
- Cause code: 241
- Reset type: Reset button
- Possible cause: Sensor disconnected or damaged (the boiler will block for 300 seconds before this condition)
D1: Return temperature too high
- Cause code: 286
- Reset type: Reset button
- Possible cause: Boiler overheat
E2: Flow sensor short circuit
- Cause code: 222
- Reset type: Reset button
- Possible cause: Flow sensor shorted or damaged
E2: Flow sensor open circuit
- Cause code: 223
- Reset type: Reset button
- Possible cause: Flow sensor disconnected or damaged
E5: Flow temperature too high
- Cause code: 218
- Reset type: Reset button
- Possible cause: Primary flow sensor overheated
E5: Primary flow sensor has exceeded 110°C
- Cause code: 332
- Reset type: Reset button
- Possible cause: Primary flow sensor overheated
E9: Safety sensor temperature too high
- Cause code: 219
- Reset type: Reset button
- Possible cause: The main heat exchanger has overheated. Maximum temperature 105°C
E9: Safety sensor short circuit
- Cause code: 220
- Reset type: Reset button
- Possible cause: Maximum temperature sensor on the main heat exchanger has failed
E9: Safety sensor open circuit
- Cause code: 221
- Reset type: Reset button
- Possible cause: Maximum temperature sensor on the main heat exchanger has not been recognised
E9: Max temperature thermostat activated
- Cause code: 224
- Reset type: Reset button
- Possible cause: Flue gas thermostat overheat
EA: No flame detected after ignition
- Cause code: 227
- Reset type: Reset button
- Possible cause: Failure of four ignition attempts. The boiler waits 30 seconds before another attempt is made
EA: Loss of flame signal during operation
- Cause code: 229
- Reset type: Reset button
- Possible cause: An established flame has been extinguished. This could be caused by:
– Moisture in the sump, due to a blocked sump/condensate trap
– A strong wind into the flue
EA: Gas valve error
- Cause code: 234
- Reset type: Reset button
- Possible cause: Gas valve coil disconnected
EA: Ignition timing error
- Cause code: 261
- Reset type: Reset button
- Possible cause: Flame not established during the first 4 seconds ignition period
EA: Too many short burner starts without confirmation
- Cause code: 338
- Reset type: Reset button
- Possible cause: There is an error where the pump is not detecting water – check pressure gauge and repressurise to 1 bar
Worcester Bosch fault codes: blocking errors
A1: Pump stuck or running in air
- Cause code: 281
- Possible cause: Little or no water in the system – check pressure gauge and repressurise to 1 bar
C1: Airflow stopped during operation
- Cause code: 264
- Possible cause: Fan has stopped
EA: No ionisation detected after ignition
- Cause code: 227
- Possible cause: No flame is detected. The boiler will block during 4 attempts before going to Locking fault
EF: Central heating, boil detect – Large delta T despite minimum burner
- Cause code: 349
- Possible cause: The boiler is operating at minimum burner load and there is a greater than 18°C Flow & Return temperature difference
No code: Safety or flow temperature rises too fast
- Cause code: 212
- Possible cause: Air lock or reduced water content – check pressure gauge and repressurise to 1 bar
No code: Temperature difference between supply and return exceeding limit
- Cause code: 213
- Possible cause: Air lock or reduced water content – check pressure gauge and repressurise to 1 bar
No code: No temperature rise after burner starts
- Cause code: 260
- Possible cause: Sensor disconnected or no water content – check pressure gauge and repressurise to 1 bar
Experiencing problems with your Worcester Bosch boiler? Our expert repairs team are on hand to diagnose the issue and will aim to get things working again in no time. Alternatively, click here to get a new boiler quote.
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