Medium
F.91 on Vaillant ecoTEC Plus 610

Your boiler is struggling to read the temperature of your hot water cylinder because there is a faulty connection or wiring issue with the sensor responsible for monitoring it.

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: Cylindertemperature sensor. 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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