BoilerFaultCodesYour boiler has switched itself off because internal sensors have detected it is getting too hot, which is a safety measure to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Overheat Lockout
What causes this fault?
This fault occurs when water inside the boiler isn't moving away fast enough, causing the temperature to rise to dangerous levels. The most common reasons are a failed pump that can't circulate the water, or a blockage within the system pipes or heat exchanger that restricts flow.
This fault is more frequent when you first turn the heating back on in autumn, as internal pump parts can seize up after months of inactivity during the summer.
DIY fix possible
Check that all radiator valves are fully openEnsure there are no blockages or trapped air by bleeding your radiatorsOnce the boiler has cooled down, press the 'Restart' button on the front panel
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like L01 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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