The boiler has a 'notorious' problem with the main pcb, BUT be careful, this fault on the pcb can be caused by the fan. If you fit a new pcb without checking the fan, you can blow the new pcb immediately (as I have learned to my cost).
There is a 3.5 amp fuse on the front of the pcb, needs to be checked.
I can't go into specifics, because resistances on the fan motor need to be checked BEFORE ordering a new (expensive £270 pcb). It is an expensive boiler when it goes wrong, you have my sympathies, whoever fitted you that piece of C**p needs to answer for it.
Carefree
July 2010