iComfort
Continuous Fan Operation
Thermostat fan runs continuously even when system is not heating or cooling
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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
Fan mode set to On or Circulate, Stuck fan relay on indoor unit control board, G terminal shorted to R, Misconfigured continuous circulation setting
How to Fix / Troubleshooting
Safety first: Turn off power to the furnace/air handler before working on wiring.
- Step 1 – Check fan mode: On the thermostat, ensure the fan mode is set to Auto, not On or a high circulation setting.
- Step 2 – Inspect G wiring: Remove the thermostat and check that the G wire is not touching the R terminal or any other conductor.
- Step 3 – Isolate thermostat: At the indoor unit, disconnect the G wire from the thermostat. Restore power. If the fan still runs, the fan relay on the control board is likely stuck closed.
- Step 4 – Replace control board: If the fan relay is stuck, replace the indoor unit control board.
- Step 5 – Replace thermostat: If the fan stops when G is disconnected but runs whenever the thermostat is connected and set to Auto, the thermostat may be sending a constant fan signal and should be replaced.
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Repair Difficulty
Medium
3/5
Required Part
Indoor Unit Control Board or iComfort Thermostat
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