Medium
9C on Viessmann Vitodens 300-W

Your boiler has lost its connection to the sensor that monitors the temperature of your hot water cylinder, meaning it cannot properly manage your hot water supply.

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: Cylinder temperature sensor lead break

Engineer required

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

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Related fault codes

9BView →9FView →A7View →

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