BoilerFaultCodesYour boiler started to heat up but the flame went out unexpectedly, causing the system to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Loss of flame during operation.
What causes this fault?
This fault occurs when the boiler successfully lights but then loses its flame while it is supposed to be running. It is often caused by a dirty or worn-out sensor that can no longer 'see' the flame, or by an unstable gas supply that prevents the fire from staying lit. In some cases, internal debris or a failing control board can also interrupt the combustion process.
This fault can be more frequent during extreme cold spells if the external gas regulator is affected by the temperature or if a high demand for heating puts extra strain on older components.
DIY fix possible
Check that your gas emergency control valve is open and other gas appliances are working.Verify if you have credit on your prepaid gas meter.Press the reset button (indicated by a flame with a line through it) to see if the boiler restarts.
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 F4 — no call-out fees, no surprises.
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Glow-worm Xtramax HE 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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