E7
Google Nest
O/B (Reversing Valve) Wire Error on Heat Pump System
Nest thermostat displays E7 and may not control heating or cooling correctly
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
O/B wire not detected or loose, O/B wire connected to wrong terminal, Incorrect heat pump type selected in Nest settings, Broken O/B conductor in thermostat cable
How to Fix / Troubleshooting
Safety first: Turn off power to both indoor and outdoor units at the breaker.
- Verify heat pump system: Confirm your system is actually a heat pump (outdoor unit provides both heating and cooling via a reversing valve).
- Inspect O/B wiring at Nest: Remove the Nest display and ensure the O/B wire is fully inserted into the O/B terminal. Re-strip and reinsert if necessary.
- Check O/B at air handler/heat pump board: At the indoor unit, locate the O/B terminal and confirm the same-color wire is attached securely.
- Confirm configuration: On the Nest, go to Settings > Equipment and verify that the system is set as a heat pump and that the O/B setting (energize in heating or cooling) matches your equipment manufacturer's specification.
- Test operation: After restoring power, test both heating and cooling modes to ensure the reversing valve is operating correctly and the E7 error clears.
If the reversing valve coil or control board output is faulty, an HVAC technician will need to diagnose and replace the defective component.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Nest Thermostat Base (O/B terminal), Heat Pump Reversing Valve Circuit
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements