Hello,
It seems if I cross the red/white wires my furnace will run all day but when I hook up a thermostat (programabel, non-prog, mercury.. etc etc, I have tried 7). It just won't keep the house warmer than 60 deg. It will turn on and off repeatedly and with some themostats just not work all together.

The strange part it, after installing a new thermostat everything seems to work fine for a few hours.

Any thoughts? Thanks.