A new circuit board was fitted about six weeks ago and all was well, but now it won't fire up. The fan is running OK and the pressure switch tubes are attatched. PCB fuse is also OK. Neon PCB light is on but no spark. Can anyone suggest a possible cause - I really don't want to replace it with an unreliable eco warrior one!

Maintenance Man, November 2008

Many thanks b, will get the switch tested and let you know how it pans out. Many thanks for your help.

Maintenance Man, November 2008

the fan starts, the air pressure switch proves the fan is
running, if the switch isn't working pcb wont generate a spark, muti-meter on the fan switch terminals might help.
also check the fan turns freely with boiler turned off
and the pipes are clear of dirt as this will stop the air
switch from pulling in

b, November 2008

Thanks but how can I tell if the pressure switch is faulty?
The air tubes from the fan are connected and OK.

I want to get a bit of an idea whats wrong before getting someone in again.

Maintenance Man, November 2008

is the pressure switch ok

b, November 2008