Worcester Bosch Fault Codes


Worcester Bosch Fault Codes


Fault Description

Possible Cause

Locking Error If there is a locking error, there will be a flashing fault code as well as a warning triangle and a static cause code. Pressing the reset button will be required to eradicate the fault.
Blocking Error

If there is a blocking error, no data will be displayed but your boiler will stop operating. By pressing the return/spanner button, you will be able to find the cause code. If for example, the boiler is waiting for an action such as the cooling of an area, the error will automatically resolve once this is done.

Fault Error A fault code is an alpha numeric code that will offer you an indication to the error by telling you the fault group.
Cause Error

A cause error code will be a three digit number, found when locating the block error.

Maintenance Code A maintenance code (beginning with H) will tell you when there is a situation that will not stop the boiler operating, but will need the attention of an engineer.


Locking Fault Code

Possible Cause


Boiler has been fitted with incorrect Heat Control Module (HTM).


The code plug could be faulty or not properly connected.


You need to replace the control board.


The system is running too fast or too slow.


Fan is not running or the airflow could be blocked.


Sensor could be wet, damaged or disconnected. The boiler will block for 300 seconds.


Boiler is overheating.


The Flow sensor has shorted, is damaged or disconnected.


The primary flow sensor has overheated.


The main heat exchanger has overheated as the main temperature is 150 degrees.


Maximum temperature sensor on the main heat exchanger cannot be recognised or has failed.


The flue gas thermostat has overheated.


Failure after four ignition attempts. The boiler will wait 30 seconds before another attempt is made.


A flame has been extinguished due to either moisture in the sump, a blocked sump or strong wind in the flue.


Gas valve coil has been disconnected.


Flame has not extinguished within first 4 seconds of ignition.


There is an error as the pump is not detecting water. Check the pressure gauge and re-pressurise to 1 bar.



Blocking Fault Code

   Possible Cause


      Little or no water in the system- Check pressure gauge and re-pressurise to 1 bar.


      Fan has stopped.


      No flame is detected and so the boiler will block during 4 attempts before going to Locking fault.


      The boiler is operating at minimum burner load and there is higher flow temperature of 18 degrees.


      Sensor has been disconnected or there is no water content- check pressure gauge and repressurise to 1 bar.




Bing Digital