Emergency
F.27 on Vaillant Ecomax Condensing 600/800 series

Your boiler has detected a flame when it is not supposed to be lit, which is a safety lock-out to prevent potential issues.

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.

Technical description

Stray light (flame signal present but gas valve closed)

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.28View →F.29View →

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