Medium
F.46 on Vaillant ecoTEC sustain

Your boiler has detected an electrical fault with the sensor that monitors the temperature of the incoming cold water, preventing it from calculating how much heat is needed.

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.

What the manual says

Manufacturer manual

Short circuit: Additional temperature sensor at the water inlet

From this model's manual
Verified against the Vaillant Ecotec Sustain installation & service manual, page 51.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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