pilot on ok, fan runs low speed and high speed ok,
but boiler will not fire up either on hot water or central heating can you help, ps have fitted new gas valve.
could it be that the pcb board is faulty have checked 24 volt supply from board to valve seems ok yet boiler wont go to main gas heat, ?

mark robinson CITB EITB, January 2009

Hi
I had the same problem with my boiler and I re-soldered some suspect connections on the board and Ta-Da.... works again.
Must have come loose after all the years in use.

Drew, January 2010

If air pressure switch is good check for bad joints on the pc board. The boards are repairable with a small soldering iron and a steady hand. ittermitant faults and arcing/sparking are sure signs. Always isolate electrical supply before working on boiler.

polaraxe, October 2009

Sounds like it could be an air problem possibly.You say the fan runs so thats good. Make sure that the boiler front cover is correctly sealed with no air leaks. If all seems sound and the fan is running the air pressure switch should operate next. Maybe the air pressure switch is faulty it operates a small microswitch along side itself when air enters a bellows type arrangement in the air pressure switch component. Make sure its switching and sending a live before replacing any more parts. Hope this helps.

polaraxe, October 2009