Medium
F.03 on Vaillant ecoTEC Plus 938

Your boiler has lost communication with the built-in hot water storage tank sensor, which means it may struggle to provide consistent hot water.

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 cylinder sensor actoSTOR (NTC) only in combination with F.91

From this model's manual
Verified against the Vaillant Ecotec Plus 826 installation & service manual, page 48.
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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F.91View →

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