What does the Viessmann 404 fault code mean?

Your boiler's central control module has detected a fault, which may stop your heating or hot water working until a qualified engineer checks it.

How much does it cost to fix Viessmann error code 404?

Typical repair cost for the Viessmann 404 fault is £250-500 including labour.

Manufacturer manual

HBMU heat management unit faulty

From this model's manual

Verified against the Viessmann/Viessmann Vitodens 100 W B1hf B1kf 6167586 installation & service manual.

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Boiler cover options

A cover plan would handle faults like 404: 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.

7 signs repair isn't worth it anymore.

Break-even maths on monthly cover.