BoilerFaultCodesYour boiler has switched itself off for safety because it has reached an excessively high temperature, likely due to a circulation problem.
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, causing a safety sensor to trip and shut the system down to prevent damage. The most common reasons are a pump failure that stops water from moving or a blockage within the pipework that restricts flow. In some cases, the sensor itself may have developed a fault and is incorrectly reporting a high temperature.
This issue is more frequent when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
DIY fix possible
Check that your radiator valves are fully open and not turned down.Ensure there is enough water pressure in the system by checking the gauge.Try resetting the boiler by pressing the reset button to see if it clears the lockout.
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A boiler cover plan would cover faults like F5 — no call-out fees, no surprises.
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