Boiler not firing central heating

[stevedb]

I have a central heating problem which a Corgi registered plumber is having problems diagnosing - the boiler is approx 20 year old Potterton Kingfisher II.

Pilot light was going out so thermocouple replaced on boiler. Then the thermocouple to gas valve connection split away, which has been "fixed" temporarily to avoid ordering a new gas valve in the short term.

Pilot light now OK, and when initially lit, burners fire for 15 minutes or so and heat rads up, then the burners go out and the rads go cold and the boiler pilot light continues to work, but the main burners do not kick in.

Hot water is OK except seems to be hotter than usual. The plumber reckons the pump is fine as well.

Any ideas as to the fault?

 

[ollski]

Room stat....is there 240v on the switched live when you are expecting the burners to relight?

 

[stevedb]

Ollski, thanks but not sure - How do you check this?

 

[ollski]

With a multimeter at the room thermostat, souds like you have 2 unrelated faults from here and your thermostat isn't clicking back in to call for heat after its satisfied.

 

[stevedb]

Thanks for the pointers. I'm leaning towards the room stat too as when fiddling with it last night the burners fired for a few seconds then died - guess it could be an intermittant fault - until I get to test it I won't know - damn glad it's a warm November though!!