is the gas on to the boiler
is the fan running and closing air pressure switch
have u check continuity from burner to earth
or flame ignition probes
had any work done recently ie electrical reverse polarity can cause this.
some boards for potterton were a bit suspect a while back mainley
with the suprima but think the profile had the same thing at one point
how old is the boiler.
best to get gas safe eng round to look at it
anonymous
October 2010