Heat Pump Error
Resideo Heat Pump Control or Reversing Valve Fault

Thermostat indicates 'Heat Pump Error' or auxiliary heat runs constantly

Advertisements

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Advertisements

Possible Causes

Misconfigured O/B reversing valve setting, Failed reversing valve coil, Incorrect wiring of Y and O/B terminals, Low refrigerant causing lockout

How to Fix / Troubleshooting

Safety first: Turn off power to the air handler/heat pump at the breaker before touching wiring. Do not open the outdoor unit unless you are trained.

Steps to troubleshoot:

  • 1. Verify system type: In the thermostat installer setup, confirm the system is set to Heat Pump and not conventional.
  • 2. Check O/B setting: Ensure the O/B reversing valve setting matches your heat pump (energized in cool vs heat) per the equipment documentation.
  • 3. Inspect wiring: At the thermostat, verify that Y, O/B, and Aux/E wires are connected to the correct terminals and firmly secured.
  • 4. Test modes: After restoring power, test both heating and cooling. If the system blows warm air in cool mode or vice versa, the O/B setting or wiring is incorrect.
  • 5. Monitor auxiliary heat: If auxiliary heat runs constantly, the heat pump may be locked out due to a fault; a technician should check refrigerant charge and outdoor unit operation.

When to call a professional: Heat pump control issues often require an HVAC technician to test the reversing valve, defrost board, and refrigerant system.

Advertisements

Repair Difficulty

Hard 4/5

Required Part

Heat Pump Reversing Valve Coil or Thermostat O/B Control Circuit
Check Price on Amazon

We may earn a commission from links on this page.

Advertisements