Weird Pilot Light problem...

23 Apr 2004
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United Kingdom

I have a Baxi boiler ('FS 501 OF' I think) which recently stopped working.

I thought it was the thermocouple and replaced this but still had a problem and closer investigation revealed...

The pilot light ignites no problem (from boiler being totally off), nice blue flame, keeps thermocouple nice and hot.

I turn the central heating on and the boiler ignites from pilot light no problems.

If I turn the CH off the boiler turns off leaving the pilot light.

No problems there then. However, SOMETIMES, but not all the time, when the CH is turned off the pilot light will burn a little yellow instead of blue and does not heat the thermocouple sufficiently thus turning the gas off.

Why does the pilot light sometimes burn blue and sometimes yellow?

When I light the pilot light it is ALWAYS blue. It is only ever yellow after the boiler has been on and the CH turns off (either by me or the thermostat).

Any suggestions?

Many thanks

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It's usually dirt /lack of air/blocked injector/sticky gas valve/wrong pressure. Corgi job.
I agree with Chris... The flame picture is a good starting point for the diagnosis of any gas related problem. Many things can cause a Yellow flame, and this is a CORGI related fault. Do not try to rectify this yourself as you can quite innocently make the appliance worse and/or make it a lot more dangerous.
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Thanks for the replies, however had managed to fix it by the time I got back to checking here.

It was a blocked injector.



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