F3 High

Keston F3 Fault Code

The Keston F3 fault code means: your boiler has detected that the internal component responsible for pushing air through the unit to ensure safe combustion is not spinning or communicating correctly, causing the boiler to shut down to prevent unsafe operation.. It appears on 4 Keston models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Fan Fault
Typical repair cost £250-450 (including labour)

Engineer required

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

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Keston models that show the F3 fault code

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

Source

Keston F3 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026