I have a Coleman 7900 series, direct vent forced air gas furnace that uses propane. Yesterday I noticed an unusual odor outside and discovered that it was coming from the chimney. Later the house got cool and I discovered that the pilot had went out. I relit the pilot and the furnace kicked on. I noticed an unusual smell coming from the floor vents a lot like that I had smelled from the chimney. I have a carbon monoxide detector that is in working order and it did not go off. I let the furnace run and warm the house without any problems other than the odor. When it kicked off the pilot was out again. I did not attempt to relight it. Is this possibly just a gas adjustment or a sign of something more ominous? The only problem I have had to deal with is replacing the thermocoupler several years back, otherwise it has been fine until now.

The smell coming out of the chimney is the smell of burnt gas byproduct. If you are smelling this out of your forced air supply registers, this is not a good thing. Sounds to me like you have a damaged heat exchanger, which would also explain the pilot blowing out. Many store bought carbon monoxide detectors just aren't that accurate(hate to say it, but it is definitely true).

At this point, I suggest not using the furnace At ALL, until you get a pro into evaluate the problem. As I'm sure you know, carbon monoxide can be deadly, and its just not worth taking a chance on, especially with what you have described. I hate to be the bearer of bad news, but I'm only looking out for your well being, and the others that may be in the home. Play it safe, have this looked at by a pro, it may save your life. Good luck and PLEASE let us know how things turn out. Take care, Lee.

I had a nasty feeling it was something serious. Someone else I talked to also said they thought it might be the heat exchanger. I thank you for taking the time to answer. Sounds like a new furnace for us!

Yep, hope you enjoy that new furnace.