I have had same prob since before Xmas. Now and again was starting on reset. Had a service (clean out), no good, now had a new air pressure switch fitted and nothing, will not even reset. No HW or CH will not even fire up.Seems to be mostly when cold temp outside. I am thinking maybe this overflow or trap maybe frozen. Where is it? I was told clean Venturi, check plastic pipes, maybe pressure switch failing, pcb.
Nacol
January 2011