Boiler was out of service whilst building work completed. Boiler was recommissioned but fails to fire.
From Mains ON and CALL for heat, Pump starts, Fan starts, gas valve ON, ignition sparks, but no burn, then flame failure light comes ON.
Injector looks clean, spark tested with external gap, good quality spark. Venturi to presure valve checked clean.
Ideas please

Grumpy, November 2009

Did you get to the bottom of this as this is exactly what mine is doing? The fan must be ok and triggering the pres switch as with out this the pilot will not light. I have 6 months ago had the gas valve and pcb replaced and reluctant to spend any more on it as most of the central heating companys have no idea how the boilers seem to work and spend more time going round in circles.

hearbear, January 2010

Hi Grumpy.
Their is just a possibility that your problem might be the fan not running at the speed required to operate the air pressure switch,this fan is vertically mounted and if it is not free running it will not initiate the pressure switch and this will cause the flame failure light to come on.
Hope this helps.

Happy, December 2009