I have a Trane XV95 furnace/air conditioner, 2 years old. It has recently been blowing out air that smells like an old refrigerator (freezer) when you had to defrost it manually. I removed the panel and the coils are not frozen. The condensate line appears to be working, but not as much liquid seems to be coming out of it as usual. The filter is not clogged up. Does anyone have any idea what may be causing the defrosting smell?