Lennox G12 Wont stay lit

[tbird]

I have a Lennox G12 that won't stay lit. You can light the burner, turn the gas valve to the run position, the burners will light and burn for a few seconds. Then about the time you would expect the blower to turn on, the flames all go out ( burners and pilot light). I also noticed the gas valve won't turn back to the "OFF" position. I'm guessing the gas valve, but then why do the burners light? Can anyone please give me some advise on this?

Any help would be appreciated.

Thanks!
TBird

[tbird]

Im sorry, have I missed something?
Is there some reason nobody will respond to this post?

[Narroc]

Sounds like the thermopile is giving problems,
1) Whats the pilot flame like, If it's not strong enough the t/p won't generate enough power to hold in for long.
2) If the pilot flame is ok then it could be the t/p is getting old.
3) The gas valve won't turn back to the off/pilot position until about approx 5 mins after the pilot has turned off. This a safety measure to allow accumulated gas to clear so the thing doesn't go bang.
4) Actually I'm not familar with the G12 but it may have a 24volt valve in which case it will have thermocouple to the pilot. If so then I would suspect the t/c or the pilot flame.
However if you don't know much about the furnace I would suggest you get an experienced gas guy to sort it out.