I have a 13 SEER heat pump about one year old. Everything's been working fine, but the AC suddenly started heating my house spontaneously (no changes to thermostat, etc).
The outside ambient temperature is 80°F but the incoming air measures 116° at the vent. The odd part is that the outside condensing unit is blowing 68°F (cold?).
What might be causing this?
Best Answer
Check the thermostat O (orange) terminal with a multimeter to ground. Most brands energize (apply 24V AC on the terminal) in cooling mode. A bunch of things could be going on such as a wire loose, bad thermostat, bad control board in heat pump or bad reversing valve but the first thing to check is the thermostat then you can work your way back to the heatpump.