my boiler works now and again, (usually not), i turn on water and the fan wont run i turn off water and the fan runs! (for a short time). if i leave the water on the red light flashes rapidly and boiler shuts down. same for heating. had plumber out hes stumped apart from pcb powered fan it runs independently,isolated water pressure switch ditto overheat. no joy if i knew for certain it was the pcb i would be happy

raymond, August 2009

if the fan runs for a few seconds when there is a demand then stops it sounds like it's the pcb. that's a common fault on the worcester 24/28si2 models which are very similar.

Ian, August 2009

Hard to know for certain sometimes, a proffesional engineer would carry a PCB and if it was the wrong diagnosis, then well.. nothing lost!

In the case of your boiler if the water flow switch has been proven, then it is likely to be the PCB

www.elanar.co.uk, August 2009