BoilerFaultCodesYour boiler has shut down because its internal temperature has become too high, often caused by a lack of water flow or a blockage.
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 the water inside the boiler gets too hot, triggering a safety sensor to shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving or a buildup of sludge and debris that creates a blockage in the pipework.
This issue is frequently seen when homeowners turn their heating back on for the first time in autumn, as pump central shafts can seize up after being idle during the summer months.
DIY fix possible
Check that your boiler pressure is between 1 and 1.5 bar on the gaugeEnsure all radiator valves and the isolation valves under the boiler are fully openPress the 'Restart' button on the front 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 4.2 — 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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