hi, i think this could be a faulty condensate trap or pcb fault, as i have something similar with one of my customers boilers. i found the condensate pipe was frozen, causing the trap to overflow and short the terminals at the top.if this isnt the fault with yours, then the next things will be the white sensor lead on top of the trap, or pcb fault.i would always reccomend getting a gas safe registered engineer in to work on your boiler, as he will have the know how and tools for the job, good luck and post back if this has helped, cheers
phil.
January 2010