heat turns pilot light off

tclarkmd · 10-11-2007, 08:41 PM

Hello, all. I have spent the better part of this last week trying to figure out why my Williams natural gas wall heater (cerca 1970's) pilot light went out this last week. There was a cold snap, and I happened to be standing at the thermostat when the heater tried to kick on. There was a brief flash of the burners igniting in a normal fashion, then they turned off. I looked inside and found the pilot off, so I tried to relight the pilot, but it will not stay lit if I release the pilot button. This furnace uses the old 2 wire millivolt system and pilot generator (PG9 type). I cleaned the pilot and generator. I turned up the pilot flame. I tried removing the thermostat wires to see if it was grounding out, but that did not help. I got a millivolt meter, and the generator is putting out about 750mV. The pilot would still not stay lit once I released the pilot button. I wasn't sure if there was enough current (what is the current produced by these generators anyway?), so I hooked a 1.5V C battery up to the millivolt connections. Wow, the pilot stayed lit with that much voltage. So I bought another generator and now have both generators together in there putting out about 1000mV (1V) which seems to keep the pilot lit. But the pilot still goes out when I turn on the heat (ie. when I turn up the setting on the thermostat to trigger the burners to ignite, or if I jump the thermostat terminals) and the main burners never light. What's up? Bad gas valve or some kind of short?

dmaceld · 10-11-2007, 10:20 PM

Possibly a burned out combustion chamber that causes the flame and air flow to be all screwy blowing out the pilot flame. A furnace that old is probably shot.

Does the pilot stay lit with battery power when the furnace fires up?

tclarkmd · 10-12-2007, 02:33 AM

hmmm. I did not try to fire the burners with the battery power to the gas valve. I was afraid if the pilot went out with the battery hookup then the gas from the pilot would keep flowing out.... Seems a bit risky. I'll post back with any other results. Thanks!

dmaceld · 10-12-2007, 10:37 AM

Quote:

Originally Posted by tclarkmd

hmmm. I did not try to fire the burners with the battery power to the gas valve. I was afraid if the pilot went out with the battery hookup then the gas from the pilot would keep flowing out.... Seems a bit risky. I'll post back with any other results. Thanks!

You're right, it is a bit risky. Just be sure to stay close by and keep watch. The reason for doing that is it would make it clear if it is a problem with the pilot light voltage, or if the pilot is getting blown out by the main flame.