What does the Vaillant F.03 fault code mean?

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

How much does it cost to fix Vaillant error code F.03?

Typical repair cost for the Vaillant F.03 fault is £120-250 including labour.

Manufacturer manual

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

Shared across the ecoTEC plus range

This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.

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

Boiler cover options

A cover plan would handle faults like F.03: no call-out fees, no surprise bills.

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Seeing a different code? Every code this model can display, in one place.

Almost always a stuck diverter valve on a combi.

Break-even maths on monthly cover.

7 signs repair isn't worth it anymore.