Emergency
F.56 on Vaillant ecoTEC exclusive

Your boiler has detected an issue with the fuel-to-air balance that could affect safe operation, so it has safely shut itself down to prevent any risk.

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

Safetyswitch-off:COlimitexceeded Safetyshutdown:COlimitvalueexceeded Acomponentinthecombustionregulationisdefective – Contactfaultatthegasvalveassembly(plugnotpluggedincor- rectlyornotpluggedin,plugdefective,slotisdefective(loosecon- nection)) – Ifthefaultoccursagainafterbeingreset:Thegasvalveassemblyis defective

From this model's manual
Verified against the Vaillant Ecotec Exclusive installation & service manual, page 56.
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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Related fault codes

F.55View →F.57View →F.28View →

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