Emergency
D.118 (8) on Vaillant ecoTEC exclusive

Your boiler's internal sensor responsible for monitoring combustion safety is reporting an electrical reading that is outside of its expected normal range.

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

CO sensor fault number: Standby reference resistance not OK

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.75View →

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