BoilerFaultCodesVaillant F10 Fault Code
The Vaillant F10 fault code means: your boiler has lost signal from the sensor that monitors the temperature of the water returning from your radiators.. It appears on 2 Vaillant models in our database.
Technical description: Central heating return NTC fault
What causes the Vaillant F10 fault?
This fault occurs when the boiler's internal computer loses communication with the sensor that measures the temperature of the water coming back from your radiators. The most common reason is that the sensor itself has developed an electrical failure, or the wiring connecting it to the main control board has become loose or damaged.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Vaillant models that show the F10 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant F10 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