How much does it cost to fix Vaillant error code F.10?

Typical repair cost for the Vaillant F.10 fault is £90-160 including labour.

F.10 High

Vaillant F.10 Fault Code

Q: What does the Vaillant F.10 fault code mean?

Your boiler has stopped working because it has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit.

Also written as F10 — same fault.

The Vaillant F.10 fault code means: your boiler has stopped working because it has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit.. It appears on 53 Vaillant models in our database.

Technical description: Flow temperature sensor short-circuit

What causes the Vaillant F.10 fault?

This fault occurs when the electrical signal from the sensor that monitors the outgoing water temperature is interrupted, usually due to a physical failure inside the component. The most common reason is that moisture or heat stress over time has damaged the sensor's internal wiring, causing it to send an incorrect 'short-circuit' signal to the main control board. If the sensor cannot safely report the temperature, the boiler will shut down as a safety precaution.

Typical repair cost £90-160 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Vaillant models that show the F.10 fault code

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

Source

Vaillant F.10 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

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