Goodman
Miswired Thermostat or Control Board
Thermostat calls for heat but outdoor AC condensing unit also runs when furnace is on (in heating mode).
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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.
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Possible Causes
Y and W wires shorted together, Incorrect thermostat wiring, Stuck relay on control board, Misconfigured heat pump thermostat on gas furnace
How to Fix / Troubleshooting
Safety: Turn off power to both furnace and outdoor unit before working on low-voltage wiring.
Steps:
- Check thermostat type: Ensure the thermostat is configured for a conventional gas furnace, not a heat pump, unless system is designed as such.
- Inspect wiring at thermostat: Confirm that W is connected only to the furnace heat terminal and Y only to the cooling terminal. No jumpers should tie W and Y together unless specified.
- Inspect wiring at furnace board: Verify that thermostat wires are landed on the correct R, W, Y, G, C terminals per Goodman diagram.
If wiring is correct and the AC still runs with heat, the control board may have a stuck Y relay and should be replaced.
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Repair Difficulty
Medium
3/5
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