Ultimate Glwwm 40FF - momentarily cutting out and reigniting

[dunkinbiscuit30]

Need a bit of guidance to help my corgi man find the fault as he has tried new pcb board and fitted new control thermostat but boiler still keeps cutting out momentarily and reigniting, (along with an annoying bang), sometimes at about 1 sec intervals, then clears until another time...especially when return starts getting hot and approaching temp cut out.
So all thats left is
air switch
electrode
solenoid
................?
Boiler man is losing will to live with this fault so any advice based on anyones past experiences gladly taken? (other than get a new plumber!) He is coming back later this week so needs some inspiration.
Thanks

 

[Deleted member 105431]

a trapped HT lead (part of electrode) arcing out on the case door is a classic cause of this. Just insulating it with electrical tape usually sorts it.

 

[dunkinbiscuit30]

Thanks for advice - it looked promising and I insulated it all up, but same thing keeps happening!
I think it may be a call out to Glowworm - its just they charge £250 call out which if it is something simple will be hard to swallow.
Apparently that charge covers anything wrong with boiler incl parts and labour so if only a wire loose or arcing then it seems a bit on expensive side.

 

[superdupergasman]

BG will be £170 - £200 dependant on your location for a fixed price repair.

I would be looking at a dirty pilot light not enveloping the ignition electrode enough.

When stripping these out to clean it a 50/50 whether the pilot supply tube will snap...worth left to a proffesional.

 

[Deleted member 105431]

Thanks for advice - it looked promising and I insulated it all up, but same thing keeps happening!
I think it may be a call out to Glowworm - its just they charge £250 call out which if it is something simple will be hard to swallow.
Apparently that charge covers anything wrong with boiler incl parts and labour so if only a wire loose or arcing then it seems a bit on expensive side.

its £215