Medium
F.003 on Vaillant ecoTEC plus

Your boiler has lost the connection to the temperature sensor in your hot water cylinder, so it doesn't know when your hot water is up to temperature.

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

The signal for the cylinder temperature sensor has been interrupted.

From this model's manual
Verified against the Vaillant Ecotec Plus installation & service manual, page 80.
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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