Baxi Fan Overrun / Stuck Relay

Furnace fan runs continuously even when there is no heat demand

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

PCB fan relay stuck closed, Overrun timer set excessively long, Faulty temperature sensor keeping fan on, External control wiring backfeeding

Safety: Isolate power before accessing the PCB.

Check controls: Ensure there is no call for heat from the thermostat or external controls.
Observe overrun: Some Baxi models run the fan for a short period after burner shutdown; this is normal. If it never stops, there is a fault.
Inspect PCB: A technician can test the fan relay on the PCB and replace the board if the relay is stuck.
Sensor check: Verify that flue and overheat sensors are reading correctly and not falsely indicating high temperature.

Hard 4/5

Main Control PCB

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