Medium
F.91 on Vaillant ecoFIT Pure 825

Your boiler is having trouble communicating with the temperature sensor in your hot water cylinder, which means it may not be able to heat your taps or shower 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

Short circuit: Cylinder temperature sensor

Engineer required

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

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