Fondital Fan Overrun / Stuck Relay

Boiler fan runs continuously even when there is no heating or hot water 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

Stuck fan relay on Fondital main PCB, Faulty flue gas sensor keeping fan on, Incorrect wiring or external control signal, PCB software fault

Safety: Continuous fan operation is usually not dangerous but indicates a fault. Noise may be disturbing.

User checks:

Demand status: Ensure all thermostats and hot water taps are off.
Power cycle: Turn the boiler off at the mains for 30 seconds, then back on to reset the control.

Technician actions:

Test the flue gas temperature sensor and other safety sensors.
Check for a stuck fan relay on the main PCB and replace the PCB if necessary.
Verify there is no external control signal forcing fan operation.

Hard 4/5

Main Control PCB

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