High
F.33 on Glow-worm 38cxi

Your boiler has stopped working because the fan is unable to clear air from the system or a sensor has detected an issue with the air pressure.

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 frost protection function active – air pressure switch fault

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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