L6 Emergency

Keston L6 Fault Code

The Keston L6 fault code means: your boiler has detected a flame when it should be switched off, so it has safely shut itself down to prevent a fire or safety hazard.. It appears on 3 Keston models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: False Flame Lockout
Typical repair cost £150-300 (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 L6 fault code

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

Source

Keston L6 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