BoilerFaultCodesYour boiler has shut itself down for safety because it either got too hot or failed to light the gas properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler has entered lockout mode. Can be caused by the overheat cut-off going open circuit or failure to detect flame.
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the unit has become dangerously hot or that the gas has failed to ignite after several attempts. The most common reasons are a lack of water circulation causing the heat exchanger to trap too much heat, or worn-out ignition parts that can no longer create a spark to light the burner.
This issue is more frequent during the first cold snap of autumn when pumps that have been idle all summer often seize up, leading to immediate overheating.
DIY fix possible
Locate the reset button (often marked with a flame symbol or 'R') on the control panelPress and hold the reset button for several seconds and wait for the boiler to restartCheck that your gas pre-pay meter has credit and that other gas appliances like your hob are working
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 Red lockout neon (lit) — no call-out fees, no surprises.
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Glow-worm Swift Flow 100 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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