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I have the Coleman model DGAA077BDTA Gas furnace. We have been having this problem off and on since its first winter in 2002.
The light says combustion failure yet it does indeed light. It will light, heat for about 2 minutes (sometimes) and then just go out. During the winter of 2005 it was recommended here that we try the flame sensor which I did. This did nothing to remedy the problem so we had our propane gas supplier recommend a service company. The company kept promising but never did make it out to work on the furnace so we ended up going thru the balance of 2005 and all of last winter with a full 350 gal. tank and heating with electric heaters. Actually saved money though. We have called another company from about 40 miles away now and they are having trouble diagnosing the problem. It still says combustion failure, still lights, goes right out, tries 2 more time and gives up for awhile. They have replaced the gas valve, flame sensor again and cleaned (didn't really seem to need it) the fresh air supply from the roof. We are waiting for them to return tomorrow for the 3rd time after supposedly going back to the shop to consult with Coleman tech support. I'm doing my best to not short change their efforts and I do believe they are trying their best. This company has been in business here in North Georgia for over 40 years and the founder DOES answer our calls. I guess I'm just getting a little frustrated after having trouble with this furnace for the first 5 years of its use. I was hoping you may have some helpful suggestions as to what I may ask they check if they don't happen to think of it. Is it possible for them to by-pass the flame sensor to verify that it is indeed working or that we may have just by chance gotten 2 bad replacements? Our gas supplier doesn't need any help with off-site storage and that is starting to seem like what I doing with enough gas to keep our kitchen range supplied for 40 years just sitting out there in the ground.
Thanks very much for any suggestions you may be able to offer.
Has anyone considered that the furnace may possibly have a bad control board? If the flame sensor wasn't working at all, the burner would go out within seconds, not 2 minutes.
Maybe Robert has some ideas . . . which I'm sure he'll be responding shortly.
Mark, thanks for your suggestion and since that is what had to be done when it went out the first time (under warranty that time) I would not be surprised that this is what is causing the problem. I see pdl2 is having the same problem as we have endured for 5 years. Is the control board a complicated install? I may be doing it myself as our hvac contractor didn't show today and didn't call either. I'm sure they will be calling though, the tech didn't bother collecting for the time or material to replace the gas valve. Is the part no. on the board itself or is it located somewhere else on the equipment.
Once again, thanks for you time and help.
B Budde
I just returned from more furnace technical training, and I think I may have learned the real cause of your problem. Oddly, this same problem came up between me and another tech attending the class.
Before the burner goes out, does the flame get real dark? If so, what's happening is that it's trying to reburn its flu gasses. This is happening because there is a break or crack in the middle flu pipe of the roof jack.
A roof jack has an inner and outer pipe. The flu gasses exhaust thru the inner pipe. If that pipe has separated, it would cause those gasses to pull back down into the furnace thru the outter pipe causing the situation you described.
The other issue may possibly be that during construction of the home, something has fallen down inside the roof jack and is partially blocking the exhaust coming out of the heat exchanger. But I think my first scenerio with the roof jack is what your problem is.
So do an inspection of your roof jack and please let us know.
Mark, I wish someone would have suggested looking down the vent pipe in Jan of 03- That is exactly what it was. The tech came back yesterday morning armed with the same advice from a Coleman tech and found a small (maybe 3 sq. in.) piece of drywall from the ceiling that had been there from the git go. As soon as they removed it everything has been working fine. As luck would have it we had our first night in the 30's last night. I really do appreciate you help with this, especially showing your true dedication to this site by taking a posters questions/challenges to a training seminar for follow-up. That's going beyond what most of us would normally expect. Thanks again.
