Overheat Lockout High

Keston Overheat Lockout Fault Code

Also written as OVERHEATLOCKOUT — same fault.

The Keston Overheat Lockout fault code means: your boiler has switched itself off because it has reached a temperature that is too high, often caused by low water pressure or air trapped in the system.. It appears on 6 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: 1 Fill system to 1.0 bar - 2 Bleed radiators - 3 Check radiator valves open - 4 Reset boiler - 5 Contact Installer
Typical repair cost £0-180 (including labour)

DIY fix possible

Check the pressure gauge and refill the system to 1.0 bar if it is too lowBleed all radiators to remove trapped air and ensure all radiator valves are fully openPress the reset button on the boiler control panel

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Keston models that show the Overheat Lockout fault code

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

Source

Keston Overheat Lockout 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