Thermostat displays E7 and fails to control heat pump defrost or auxiliary heat correctly

Safety first: Turn off power to both indoor and outdoor units at their breakers before working on thermostat wiring.

Steps to troubleshoot E7 heat pump control:

• 1. Verify system type: In the thermostat installer setup, confirm that the system is configured as a heat pump with or without auxiliary heat, matching your Goodman outdoor unit model.
• 2. Check O/B setting: Goodman heat pumps typically use O (energize in cooling) for the reversing valve. Ensure the thermostat is set to energize the reversing valve in the correct mode per the Goodman heat pump documentation.
• 3. Inspect O/B wiring: At the thermostat, confirm the O/B wire is firmly connected. At the Goodman outdoor unit control board, verify the same conductor is on the O terminal. Repair any damaged cable.
• 4. Test output: With power restored and a call for cooling or heating active, measure 24VAC between O/B and C at the outdoor unit. If no voltage is present when expected, the thermostat or wiring is at fault.
• 5. Correct misconfiguration: If the thermostat was set for the wrong reversing valve logic (B instead of O), change the setting and test operation. E7 should clear after a power cycle.
• 6. Replace thermostat if needed: If wiring and configuration are correct but the O/B output never energizes, the thermostat's output relay may be defective and the thermostat should be replaced.