Emergency
S.62 on Vaillant ecoTEC Plus 826

Your boiler has detected that the fuel and air mixture used to heat your home is not balanced correctly, which may affect its efficiency and safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Gas family check unsuccessful: CO/CO₂ values at limit. Check combustion.

From this model's manual
Verified against the Vaillant Ecotec Plus 826 installation & service manual, page 48.
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 emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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