Napoleon Continuous Fan Operation

Furnace blower runs continuously even when the thermostat is not calling for heat.

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.

Possible Causes

Thermostat fan set to ON, stuck fan relay on the control board, limit switch open causing fan-only mode.

Safety first: Turn off power before accessing the control board.

Check thermostat setting: Ensure the fan switch on the thermostat is set to AUTO, not ON.
Inspect limit switches: If a high limit switch is open, the control board may run the fan continuously. Test limit switches for continuity and replace any that are open at room temperature.
Fan relay check: If all limit switches are closed and the thermostat is set correctly, the fan relay on the control board may be stuck closed. This typically requires replacing the control board.

Medium 3/5

Integrated Furnace Control Board

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