How much does it cost to fix Viessmann error code 10?

Typical repair cost for the Viessmann 10 fault is £90-180 including labour.

10 Low

Viessmann 10 Fault Code

Q: What does the Viessmann 10 fault code mean?

Your boiler's outside thermometer has developed a fault, causing the system to 'think' it is 0°C outside and adjust your heating accordingly.

The Viessmann 10 fault code means: your boiler's outside thermometer has developed a fault, causing the system to 'think' it is 0°c outside and adjust your heating accordingly.. It appears on 9 Viessmann models in our database.

Technical description: Controls according to 0°C outside temperature - Outside temperature sensor shorted out

What causes the Viessmann 10 fault?

This fault occurs when the electrical connection to the external temperature probe is broken or short-circuited. The most common reasons are moisture getting into the sensor housing, damage to the cable running along the outside wall, or the internal component simply failing over time.

This fault is often noticed during autumn or early winter when temperature changes first trigger the boiler to look for external data to adjust the heating.

Typical repair cost £90-180 (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 10 fault code

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

Source

Viessmann 10 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