Investigative Heat Pump Repair in Jonesborough, TN Solves the Issue of a Heat Pump Running Wild

Received a call from a customer in Jonesborough, TN in need of a heat pump repair. She stated that they went out of town and came home and it was over 100 degrees inside their home. She stated that their Carrier heat pump seemed to be running in heat mode even though the thermostat stated that it was in cooling mode. We advised them to turn the system off until we got over there.

When we arrived, it was very hot inside their home. We went to the thermostat and turned the heat pump into cooling mode. We felt the air coming out of the supply registers and it appeared that heat was coming from the vents. We went to the outdoor unit and the discharge air coming out of the top of the unit was cool instead of warm. We felt the suction line and it was not cool like it should have been if it was running in cool mode. It was warm instead. These symptoms told us that we were indeed running in heat mode with a call for cooling from the thermostat.

We checked incoming low voltage to the outdoor unit between “C” and “O” and we did not have an “O” call from the thermostat to the outside unit. A Carrier heat pump reverts to running in heat mode instead of cool mode if it doesn’t receive an “O” call during cooling operation. Carrier heat pumps rely on the “O” call in order to energize the reversing valve solenoid as they operate with energize in cool mode reversing valves.

Since we did not have an “O” call at the outdoor unit we moved into the basement and opened up the indoor air handler in order to locate where we were losing that “O” call. We removed the wire nuts from the low voltage “C” and “O” wiring in order to verify that we had 24 volts coming from the thermostat. The “C” wires were intact, but the “O” wires were not. The low voltage “O” wire from the thermostat was intact, but the “O” wire to the outside had broken off inside the wire nut which stopped the “O” call from reaching the outdoor heat pump. Whenever the system was installed the “O” wire maybe got stripped with too small of a wire stripper size and it had dug too deep into the copper wire. Eventually over time the connection broke with vibrations and caused the failure.

We killed high voltage power to the indoor unit and stripped the “O” wire to the outdoor unit back to expose fresh copper wire and attached it to the “O” wire from the thermostat. We put a new wire nut on that connection and made sure that the wires wrapped over on themselves as well. We restored high voltage to the system and waited on the time delay on the thermostat so that pressures would equalize inside the system. The system turned on and was blowing cool air inside the home. We put everything back together, confirmed we had cool air coming out of the supply registers, we were discharging warm air out the top of the outdoor unit, and the suction line was cool and sweating like it was supposed to be doing with a cooling call. We performed a temperature split check between return and supply and verified that we were within range for cooling operation. We offered to hook probes up to the system in order to monitor the system’s performance, but the customer declined the additional work because the system was cooling again.

If you reside within our service area of Northeast TN and are in need of a heat pump repair, please feel free to reach out to us. We are thorough in our work and would be happy to help you out. Stay safe and best wishes.

Location: Jonesborough, TN