The PCB commonly fails often giving one of the following symptoms:
Fuse on PCB blown - boiler does nothing.
Pump runs but fan not running or erratic.
Pump and fan run but gas valve doesn't open (but check air pressure switch).
Pump, fan & gas valve operate but no spark ignition.
Boiler lights but shuts down after a few seconds because it doesn't detect flame (but check electrode leads and condensate trap if conncted).
PCBs are available on Ebay.
Phil T
June 2010
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.