How much does it cost to fix Viessmann error code A8?

Typical repair cost for the Viessmann A8 fault is £180-450 including labour.

A8 High

Viessmann A8 Fault Code

Q: What does the Viessmann A8 fault code mean?

Your boiler's main internal computer has lost touch with the display panel, meaning the controls cannot talk to the heating unit.

The Viessmann A8 fault code means: your boiler's main internal computer has lost touch with the display panel, meaning the controls cannot talk to the heating unit.. It appears on 5 Viessmann models in our database.

Technical description: Communication fault between PCB and programming unit (user interface)

What causes the Viessmann A8 fault?

This fault occurs when the data link between the boiler's main brain and the control screen is broken or interrupted. The most common reason is a loose internal connection or a failure of the delicate wiring that carries signals between the two components.

Typical repair cost £180-450 (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 A8 fault code

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

Source

Viessmann A8 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