BoilerFaultCodesKeston L1 Fault Code
The Keston L1 fault code means: your boiler has failed to fire up multiple times in a short period and has locked itself out for safety.. It appears on 3 Keston models in our database.
Technical description: 5 boiler auto-restarts in 15 minutes — switch off/on at mains
DIY fix possible
Switch off the power to the boiler at the main wall switch or fused spurWait for 30 secondsSwitch the power back on to see if the boiler resets and fires up
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Keston models that show the L1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston L1 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 31 August 2026