may be faulty fan, pcb or primary thermistor. but it's most likely that the flow switch diaphragm is burst so the boiler thinks the pump isn't running. either that or your pipes are frozen which would cause the same problem. the flow switch is on top of the 3 way valve on the left hand side of the boiler. with the pump running a small pin should pop up and flick the microswitch sitting on top of it, that lets the power go to the fan etc.
Ian, January 2010
