Worcester Heatlslve 20/25 Oil Combi Blowing Internal fuse

[aje9999]

Hi , Hope someone can help.
Noticed this morniong no heat from rads although they did come on earlier this morning, I checked the boiler and there was Power light and light for Heating so I turned up the thermostat and left for 5 mins. When I checked again there wer no lights atall including power light. I check and the internal fuse on the main circuit board had blown ( 250v 3.15mAh Quick blow). I unplugged all main connectors on board and replaced the fuse. and then plugged connectors in one by one and turned power back on each time to see which one was causing the fuse to blow. It turned out to be the connector that goes into the Blue sleeving and then on to the Burner (B11) Control Box where the lockout reset button is. As soon as I plug that conenctor into the main board the fuse blows again.

1) Has any body any ideas what copuld be causing this ?
2) Are there any more tests I could do to try to isolate the problem a bit more, I dont want to replace the whole burner if its just a part of it ie Oil pump or Motor.

Any ideas would be gratefully received.
Thanks Adrian

 

[aje9999]

For the record managed to trace it to the Transformer on the Burner by disconnecting transformer in Control box and finding that the fuse did not blow. Removed transformer and it had got hot and swollen the plastic casing,changed transformer £35 and all okay.