High
F.33 on Vaillant Turbomax Plus VUW 242E

Your boiler has stopped working because it cannot confirm that air is moving through the flue correctly, triggering a safety shut-down to prevent combustion issues.

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

(837/637 only) | Main heat exchanger anti freeze protection mode due to no switching signal from the air pressure switch | Check air pressure switch, fan, fan supply or flue system

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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Related fault codes

F.32View →

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