We live in the mountains of Colorado, and needless to say, we were -23 last week, this morning it is -14. We are trying to figure out our furnace without putting out a bunch of money. Last year we replaced our thermostat, but it's still not coming on, unless we put a wet rag over the top of the thermostat. I've been replacing the batteries in the thermostat almost daily, shutting it down first, and then manually turning the thermostat on to get the heat to kick on. We have it set at 64, and it doesn't come on till it's 48. And then sometimes it will kick on, but not stay on to reach the 64. Do we need to clean a sensor in the furnace or something else? Do you have any suggestions? Why is it not heating our home to 64 without shutting down? Sometimes you can hear it "flaming on", but then it will shut right down? PLEASE help us

What kind of furnace is it? Is it an 80% or 90% efficient?