High
F9 on Viessmann Vitodens 300-W

Your boiler is failing to start because the internal fan is not spinning at the correct speed to safely clear the exhaust gases.

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

Fan starts, after approx. 51 seconds: Check cables and plug-in connections

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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