My heater/AC controls were screwed up. I had max heat (or max cool) only. The problem was in the temp control.
I tore the panel apart.
The three controls had all gotten extremely hot at some point. There was some plastic melting.
I suspect the previous owner had run the heat on high for a long period of time. Maybe to clear the windows?
I cleaned everything up, replaced the one control (less than 20 bucks) then reassembled.
Everything works fine now.