Medium
9b on Viessmann Vitodens 300-W

Your boiler has lost connection with one of its temperature sensors, meaning it cannot accurately monitor the water temperature to operate efficiently.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Control mode: Sensor S3 lead break

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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