High
S.33 on Vaillant aquaPLUS

Your boiler is struggling to breathe properly because it has detected a problem with the air being pulled in or the exhaust fumes being pushed out.

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.32View →F.33View →

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