High
S.33 on Vaillant ecoTEC plus Aquaplus

Your boiler is struggling to breathe because it has detected an issue with the air intake or exhaust system.

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

Check air/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.33View →F.28View →F.29View →

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