Medium
A7 on Viessmann Vitodens 100-W

Your boiler is struggling to accurately detect the temperature of your hot water cylinder, which may result in your hot water not heating up correctly.

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 unit fault - hot water - check the cylinder temperature sensor

Engineer required

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

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Related fault codes

A9View →

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