BoilerFaultCodesYour boiler has shut down because it has detected it is getting too hot or there isn't enough water moving through the system to keep it cool.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow temperature overheat lockout or no water flow lockout
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature limit or stops moving entirely, triggering a safety shutdown to prevent damage. The most common reasons include a seized pump that isn't circulating the water, a blockage in the pipework caused by sludge, or a faulty sensor that is incorrectly reporting the temperature.
This issue often surfaces when the heating is first turned on in autumn, as central heating pumps can seize up if they have been left inactive throughout the summer.
DIY fix possible
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 barCheck for any visible leaks in the pipeworkPress the Reset button on the front of the control 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 L1 — 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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