Attack Stuck Fan Relay / Post‑Purge Control Fault

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

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.

Possible Causes

Stuck relay on Attack main PCB, Incorrect control parameter for post‑purge time, Faulty flue gas sensor keeping fan on, Wiring short between control and fan

How to Fix / Troubleshooting

Safety: Continuous fan operation is usually not dangerous but indicates a control fault.

Steps:

Power cycle: Turn off power for a few minutes, then restore. If the fan starts immediately with no demand, a control fault is likely.
Check external controls: Ensure no external signal is falsely calling for heat.

Technician: A service engineer should test the PCB and associated sensors and replace the board if necessary.

Repair Difficulty

Hard 4/5

Required Part

Main Control PCB

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