this boiler recently stopped lighting up - i spoke to a freind plumber over phone and he said it could be the pcb board and the valve switch is stiuc - i was advised to tap that area and see what happens - the fan is on but no flames - whilst hovering the dust and webs away i touched one of the cables - not sure which but under the igniter genearator and then the boiler fired up - now when i ned to start it i have to hit it and then there is a spark and he presto - i have been told it could bethe air pressure switch as the fan is on - thinking of cleaning the rubber pipes to this - anything else i should try and if need new pressure swithch where can i get it the part number is 64220403 but baxi tell me it is an obsolete item - any help appreciated. thanks

0134franco, March 2010

check the white ignition lead that pushes in to the corner of the pcb is fully pushed on, they often get loose and stop the spark getting to the electrode

john, March 2010

I am a retired electronics service engineer - what you describe is more symptomatic of a bad connection than a bad switch - switches seldom begin to operate when tapped - can happen but very rare.

Use a wooden spoon to gently tap around to find where the bad connection may be.

I volunteer this to save you the effort & cost of finding a replacement air pressure switch - it may indeed be the APS but you can check it with a meter if you have one - it should put out 230V when it makes as the fan runs up.

I am not qualified to offer help on boilers - just on diagnosing bad connections.

Good luck...

Peccavi, March 2010