BoilerFaultCodesKeston 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 detected it is getting too hot, usually caused by a lack of water flow through the system.. It appears on 7 Keston models in our database.
Technical description: Flow Temperature Overheat Lockout - Check water pressure, radiator valves, and pump rotation.
DIY fix possible
Check the pressure gauge and top up the water if it is below 1.0 barEnsure at least two radiators are fully turned on and their valves are openReset the boiler by pressing the reset button for five seconds
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like Overheat Lockout: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
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 31 August 2026