Medium
F.12 on Vaillant ecoFIT Pure 425

Your boiler is struggling to read the temperature of your hot water cylinder because a sensor or its connecting wire has developed a fault.

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

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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Related fault codes

F.11View →F.13View →

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