L8 High

Keston L8 Fault Code

The Keston L8 fault code means: your boiler's computer system has lost its internal settings, or the main control unit itself has developed an internal electrical fault and can no longer operate.. It appears on 2 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: PCB UNCONFIGURED OR 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 L8 fault code

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

Source

Keston L8 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