BoilerFaultCodesYour boiler is trying to start up but cannot detect a flame, 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: FAULT: THE BURNER LIGHTS BUT THEN GOES OUT. THERE IS NO FLAME DETECTED.
What causes this fault?
This fault occurs when the boiler's internal computer cannot verify that a flame has successfully ignited, leading it to shut down the gas supply for safety. The most common reasons are a worn-out flame sensor that can no longer 'see' the fire, a faulty ignition lead, or a blockage in the gas valve preventing the burner from staying lit.
DIY fix possible
Check if other gas appliances (like a hob) are working to ensure gas supply is activeCheck that your credit is topped up if you have a pre-payment gas meterPress the 'Reset' button (indicated by a flame with a cross through it) and hold for 2 seconds
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 F1 — no call-out fees, no surprises.
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Glow-worm 18si 24ci 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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