Could it be it is finally giving up? When it cycles and the fan pushes the first blast of air into the house , you seem to detect a moist , sulfery smell , this happened last year when the propane tank went too low, but that is not the case. I already had to do the new heat exchanger because it went out just before the recall and the company would not back myclain. this units is about 18 years old, the heat exchanger was replace about 6 years ago and I had a tune up about a year ago
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