Well, we turned the thermestat off for a while and changed the filters then turned the therm back on and voila, hot air! So what really happened? Why would it do that? I just don't understand.

It is very possible that your filters were dirty and/or restrictive, thus reducing air flow. When this happens, temperature inside the furnace may rise to an unsafe level.

Then, the burner turns off and the fan runs to cool everything down. This is a safety feature.

What type of filters are you using and where are they located? Some pleated filters (Filtrete, 3M)can be restrictive.

V

I bet that is what happened. DH hates changing those filters even though DS and I have bad allergies. We have 1 filter headed up the stairs to the bonus room and one in the great room/living area.
How often are filters to be changed? I am thinking it would be a good Christmas gift for DH :)

It quit working again Sunday evening so I called our local repair guys and they came Tuesday afternoon. The board was bad.