Low
S.335 on Vaillant ecoTEC Plus 836

Your boiler is currently performing a safety check to ensure that air and exhaust fumes are moving through the flue pipe correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Checkingwhetherafluegasblockageispresent.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 80.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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