High
FA on Viessmann Vitodens 100-W

Your boiler has detected that the internal exhaust fan is not switching off correctly when it should, which is a safety mechanism to prevent the boiler from starting under unsafe conditions.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Burner in fault state, fan not at standstill

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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