Goodman Blower Stuck in Fan-On Mode

Blower runs continuously even when thermostat is not calling for heat or fan.

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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

Thermostat fan set to ON, Stuck blower relay on control board, High limit or rollout switch open causing safety fan mode, Shorted thermostat wiring between G and R

How to Fix / Troubleshooting

Safety: Turn off power before working on thermostat or control board wiring.

Steps:

  • Check thermostat setting: Ensure the fan mode is set to AUTO, not ON.
  • Inspect thermostat wiring: Remove the thermostat and check that no wires are touching between R and G. At the furnace, verify G is not shorted to R.
  • Check safety switches: If a limit or rollout switch is open, the board may run the blower continuously. Test these switches for continuity and correct any overheating causes.
  • Board relay: If wiring and safeties are good, the blower relay on the control board may be stuck closed, requiring board replacement.

If you are not comfortable testing live circuits, have a technician diagnose the blower control.

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Repair Difficulty

Medium 3/5

Required Part

Furnace Control Board
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