My ageing, but until now perfectly reliable, Glow worm wall mounted central heating boiler appears to have developed a fault and I would like to know if it is possible to repair, or at least diagnose the problem. When I turn on the system the water pump comes on, the boiler exhaust fan turns on, the piezo starter ignites the pilot, the main jets fire up nice and blue. All looks well for about 30 seconds and then the jets go out and there is a couple of clicks and silence. Leave it for a few minutes and the whole boiler lighting sequence repeats. I end up with vaguely warm radiators and warm tap water but nothing more. There appears to be a good forced air flow on the outside vent, and nothing appears blocked. I have replaced the circulating pump thinking that had gone. The three way valve appears to operate ok.

Martin Eglin, June 2008

Thanks Steve. I've done that but no difference. There's a good strong pilot light which does appear to bathe the ignition electrode with a sidaways flame. Does the electrode act as a flame sensor and your thinking was that it wasn't getting hot enough? Could it have failed and can I test this out of circuit with say with a test meter and flame?

Martin, June 2008

clean the pilot assy. when hot contraction occurs closing down the injector hole. prick this out with a fine needle.

steve, June 2008