Even the most reliable boilers will encounter a fault at some point in their life. To make things easy to diagnose, boilers often display an error code when they are not working. The error code can be used to identify the issue, cutting down on investigation time and aiding you in what steps to take to resolve it. In this article, we have outlined the common fault codes associated with the Worcester brand to help you on your way.
Common Worcester Bosch boiler error codes
| Fault code | System behaviour |
| 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 blocking error codes
| Fault code | Possible cause |
| A1 | Little or no water in the system – check pressure gauge and repressurise to 1 bar. |
| C1 | Fan has stopped |
| EA | No flame is detected. The boiler will block during 4 attempts before going to Locking fault |
| EF | The boiler is operating at minimum burner load and there is a greater than 18°C Flow & Return temperature difference |
| No Code | Air lock or reduced water content – check pressure gauge and repressurise to 1 bar |
| 260 | Sensor disconnected or no water content – check pressure gauge and repressurise to 1 bar |
Worcester Bosch error code EA 229 or D5
If you’re seeing the error code EA 229 or D5 on your Worcester Bosch boiler, this means that the condensate pipe is frozen.
Worcester Bosch locking error codes
| 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 |
| D1 | Sensor wet 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. |
