Recently, I'm having problems getting the furnace to blow out warm air. I have woken up in the middle of the night or returned home from work with the place at about 55-60 degrees with the furnace fan blowing (only cool air). However, if I turn the breaker off and on, the next cycle usually seems to work fine and hot air blows out. I recently installed a digital thermostat a few months ago. Could the problem be with the wiring of the new thermostat or something with the furnace itself? It doesn't seem to be doing this all the time. Any thoughts?