In message , Paul
writes

"BigWallop" wrote in message
. com...
If the boiler has an electronic ignition, then check all the electrical
connections inside the boiler control panel. Vibration from running fans,
temperature changes Etc. can cause the connector to loosen off from their
mounts. The cold boiler will spark, but if it's hot it wont, sort of
scenario.





thanks for the replies so far, the boiler has electronic ignition. i have
checked all the connections and they look ok, the only thing i have noticed
is that one of the wires going to the electrodes has a sooty deposit on it
so there may be a short to the case, does the electronic ignition produce
high enough voltages to arc through poor insulation?. looking at the wire
the insulation looks ok


does the pcb have a separate HT and flame sense lead ?

The sooty deposit will be because of electrostatic attraction around the
HT - it's a red herring

Q1 has any wiring been changed recently which would lead to the
possibility of live and neutral being arse about face

Q2 do you have bad earthing

Q3 is the sense electrode (if its not the same as the ign electrode) in
the flame

Q4 If the HT lead is used for flame sensing, is it intact ? The fact
that it will conduct a high voltage spark doesn't mean that it will
conduct the small flame sensing current

Q5 do you have a chair to sit down on when they tell you the price of a
new pcb?




--
geoff