Medium
F.78 on Vaillant ecoFIT Pure 835

Your boiler has lost the connection to the temperature sensor that controls your hot water, meaning it cannot properly heat the water for your taps.

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

Interruption to DHW outlet sensor at external controller

From this model's manual
Verified against the Vaillant Ecofit Pure 830 installation & service manual, page 34.
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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