High
S.33 on Vaillant ecoTEC exclusive

Your boiler is temporarily pausing because its internal safety sensors detect that the airflow needed to burn fuel safely is not moving correctly.

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.

What the manual says

Manufacturer manual

Waiting time: Air monitor (Waiting period: Air pressure sensor/switch reports that the pressure signal is too low)

From this model's manual
Verified against the Vaillant Ecotec Exclusive installation & service manual, page 53.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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.32View →

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