Got a bit of a weird problem with our boiler. It's a Glow-Worm Economy Plus EP40B (non-combi) with a pilot that should be on all the time.
If the external temperature is above about 0, it's usually OK. However, in the recent cold snap, and after the boiler has been running for a while (so is hot), and about 2 mins after the main burner turns off, I can hear "clunk" and the pilot light goes out.
I had the thermocouple replaced recently, so I think that's OK. (I can always re-light the pilot easily when the boiler is cold, and it will stay on until the end of the next period when the main burner is used).
It seems to be something to do with the difference with the outside air and the boiler temps.
One thing I have noticed is that only the very tip (2mm or so) of the thermocouple is red. Could a draught caused by the temperature difference be "pulling" the flame away from the thermocouple sufficiently to turn it off? Is the thermocouple in slightly the wrong position? Or could the flame not be strong enough (is there any way to adjust it)?
Ideally I'd like to solve it myself, but understand that most things should be done by the pros.