| Fault Code | Possible Cause |
|---|---|
| 9A | Incorrect HCM fitted |
| 9U | Problem with the code plug (faulty or not connected) |
| B7 | Replace control board |
| C6 | Running too fast / Running too slow |
| C7 | Fan not running / Fan not running or airflow blocked |
| D1 | Sensor wet or damaged (the boiler will block for 300 seconds before this condition) |
| D1 | Sensor disconnected or damaged (the boiler will block for 300 seconds before this condition) |
| D1 | Boiler overheat |
| E2 | Flow sensor shorted or damaged |
| E2 | Flow sensor disconnected or damaged |
| E5 | Primary flow sensor overheated |
| E9 | The main heat exchanger has overheated. Maximum temperature 105°C |
| E9 | Maximum temperature sensor on the main heat exchanger has failed |
| E9 | Maximum temperature sensor on the main heat exchanger has not been recognised |
| E9 | Flue gas thermostat overheat |
| EA | Failure of four ignition attempts. The boiler waits 30 seconds before another attempt is made |
| EA | 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 coil disconnected |
| EA | Flame not established during the first 4 seconds ignition period |
| EA | There is an error where the pump is not detecting water – check pressure gauge and repressurise to 1 bar. |
Worcester Bosch Boiler Locking Error Codes
Worcester Bosch Boiler Locking Error Codes