Medium
F.91 on Vaillant ecoFIT Pure 835

Your boiler has lost the ability to read the temperature of your hot water cylinder, which means it cannot safely heat your tap water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

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

Shortcircuit:Cylindertemperaturesensor. NTCsensordefective,shortcircuitinthecableharness,cable/casing

Engineer required

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

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