How much does it cost to fix Viessmann error code A0?

Typical repair cost for the Viessmann A0 fault is £150-300 including labour.

A0 Emergency

Viessmann A0 Fault Code

Q: What does the Viessmann A0 fault code mean?

Your boiler has detected a flame before it has actually started up, which is a safety mechanism preventing it from firing when it shouldn't.

The Viessmann A0 fault code means: your boiler has detected a flame before it has actually started up, which is a safety mechanism preventing it from firing when it shouldn't.. It appears on 2 Viessmann models in our database.

Technical description: Burner blocked, flame signal is present at burner start

Typical repair cost £150-300 (including labour)

Engineer required

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

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Viessmann models that show the A0 fault code

Click a model for the full fault code list and model-specific repair notes.

Vitodens Repair: £150-300
Vitodens 100-W Repair: £150-300

Source

Viessmann A0 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026