coleman 7680b 856 cuts off after firing.

[Daddio]

Hi guys, kind of in a tough spot here. 2+ feet of snow yesterday , snowed in with 2 babies and the furnace quits. Below zero temps outside. i am searching the forum for answers right now but thought i would also ask my specific question too. yesterday i came in from shovling and the furnace was out. very windy yesterday so i thought the pilot blew out. checked and the pilot was out , so i relit it. no problem. turn the thermostat back up, the furnace fires for belween 10 and 30 seconds, and it looks like the gas just shuts off, pilot and all. braved the blizard to goto home depot last night and got a new thermocouple. installed it. same thing. i also thought maybe the chimney/exhaust was plugged with snow , but there seems to plenty of air flow. the match usually blows out before i reach the pilot light. and when it fires it seems to have a good blue flame. its sunday and nobody is returning my calls. any help would be great. thanks

[gordo48111]

You probably don't want to hear this but if you have had 2+ feet of snow and high winds, there is a good chance that the combustion air inlet on the roof jack is covered with snow. Take a look outside. If you can't see the ring below the cap on the top, the combustion air inlet is probably blocked. Gas is exhausted through the inside flue pipe while combustion air is drawn in from the outer pipe. My neighbor has this problem when we get a heavy snow. He attached a pole to a broom so that he can reach it from on top of a ladder without having to get on the roof. Keep us informed on what you find.

[Daddio]

thank you very much. ill check that right now. where exactly is the inlet? how far up or down on the flue?

[gordo48111]

The air inlet is under a hooded ring that surrounds the outside of the pipe. It could be halfway up the pipe or closer to the flue cap. You can't miss it unless it is buried in snow.

[Daddio]

ok, cool. thanks again. ill update you as soon as i find out. if that dont work do you know of a way to get the blower to run without the furnace on? i have a few space heaters goin and it would help if i had the blower running to circulate the air.

[gordo48111]

If you don't have a "fan on" switch on the thermostat base I'm not sure if it is possible to run the blower on your model furnace. Some have a fan-limit switch that starts the blower by temperature while others have a control board that starts the blower after a delay. If yours has a control board there is a way to run the blower by itself. If Robert checks in here he will know, he is one of the moderators on this site and is the Coleman guru.

[Daddio]

finally dug the ladder out, got on the roof, and it was completly buried. dug it out and it seems to be working fine now. thank you again ,very very much. i got a wife and 4 kids that thank you too.

[gordo48111]

I'm glad I was able to help and hope there are no other problems. I am also glad you didn't fall off the roof! Have a great holiday.

[gordo48111]

By the way, you might want to keep that old thermocouple, or reinstall it and keep the new one handy for future replacement, if needed.