Thermostat displays E7 and will not operate in heat pump mode correctly

Safety first: Turn off power to the air handler and outdoor heat pump at the breaker before adjusting wiring.

Steps to correct:

• Confirm system type: Verify that your system is a heat pump and requires an O/B reversing valve connection. Conventional systems do not use O/B.
• Check O/B wiring: At the thermostat wall plate, ensure the reversing valve wire is firmly connected to the O/B terminal. At the air handler or outdoor unit, confirm the same conductor is landed on the reversing valve terminal.
• Verify configuration: In the Sensi installer setup, confirm whether the reversing valve should be energized in heating or cooling mode. This must match the heat pump manufacturer's specification.
• Inspect for shorts: Look for any place the O/B wire insulation is damaged or pinched, especially where it passes through metal knockouts.
• Test operation: After corrections, restore power and command both heating and cooling from the thermostat. Confirm that the outdoor unit switches between heat and cool correctly and that E7 does not reappear.

When to replace: If wiring and configuration are correct and the heat pump reversing valve works when manually powered by a technician, the thermostat's O/B output may be defective, requiring thermostat replacement.