sounds sus like a pcb alrite, make sure to check it at the pcb when fan is disconnected (ie. not a problem with fan motor causing the voltage to drop out) would have a better idea if you told us what boiler?
assume the boiler is locking out? you sure all stats & thermisters are ok, flow swtch is making (not comming out, momenterialy then goin back in) as this is a sign of the pump on its way, or the heat exchanger being partially blocked
try give us a fuller picture of the problem, the devil is in the detail
T, May 2008
