pilot light won't light on a PROTHERM 80e as it should

[Dave C]

i turn on the boiler and the fan kicks in straight away.the pilot light is not alight. if i remove the tube that comes from the air pressure switch at the fan end and suck on this the pilot and burner lights.i seal the end and the boiler runs ok so that i can fill a bath. i then turn the boiler off.i have to do this everytime i require hot water. Any ideas please?

 

[kevplumb]

change the air pressure switch

 

[ChrisR]

First I'd take the fan out and clean it, then retry with the original pressure switch. By the way it's easy to destroy pressure switches by sucking/blowing too much pressure.