How much does it cost to fix Viessmann error code 80:1?

Typical repair cost for the Viessmann 80:1 fault is £120-280 including labour.

80:1 Medium

Viessmann 80:1 Fault Code

Q: What does the Viessmann 80:1 fault code mean?

Your boiler has detected a persistent communication issue with its external sensors or internal control system that has lasted more than five seconds.

Also written as 801 — same fault.

The Viessmann 80:1 fault code means: your boiler has detected a persistent communication issue with its external sensors or internal control system that has lasted more than five seconds.. It appears on 5 Viessmann models in our database.

Technical description: With 5 seconds' time delay for fault message; message will be issued, if a fault persists for at least 5 seconds

What causes the Viessmann 80:1 fault?

This fault occurs when the boiler's central brain loses contact with the sensors that monitor water temperature. It is usually caused by a loose connection in the internal wiring or a physical failure within the temperature sensor itself, meaning the boiler can no longer safely verify how hot it is. In some cases, the control board may be unable to process the data it receives, leading to a total communication breakdown.

Typical repair cost £120-280 (including labour)

DIY fix possible

Navigate to the boiler control panelPerform a system reset by pressing the RESET buttonCheck for any loose external wiring if visible and safe to touch

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Viessmann models that show the 80:1 fault code

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

Source

Viessmann 80:1 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