BoilerFaultCodesYour boiler has tried to light several times but cannot detect a flame, causing the system to lock out 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: Flame not detected (40)
What causes this fault?
This fault occurs when the boiler's internal sensor fails to detect a steady flame after several ignition attempts, causing the system to stop for safety. The most common reasons are a lack of gas reaching the burner, worn-out spark electrodes that can no longer ignite the fuel, or a build-up of carbon on the sensor that prevents it from 'seeing' the flame.
This fault is more common during extreme cold snaps, as external gas meters or pipes can sometimes freeze or experience pressure drops, disrupting the steady flow of fuel required for ignition.
DIY fix possible
Check if other gas appliances in your home, like a gas hob, are working to confirm your gas supply is active.If you have a prepaid gas meter, check that you have sufficient credit.Press the 'Reset' button on the boiler control panel for five seconds to see if the system restarts.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like EA — no call-out fees, no surprises.
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