BoilerFaultCodesYour boiler is struggling to keep a steady flame alight because the gas supply is inconsistent or contains air pockets.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Unstable flame signal error air in gas
What causes this fault?
This fault occurs when the boiler's control system detects that the flame is flickering or unstable, making it unsafe to continue operating. The most common reasons are air bubbles trapped in the gas pipework after a service or a buildup of carbon on the sensing probe that prevents it from 'seeing' the flame correctly.
DIY fix possible
Check that your gas meter has credit and the isolation valve is fully openEnsure other gas appliances, like a hob, are working correctly to purge air from the pipesPress the 'Reset' button (indicated by a flame with a cross through it) once to restart the ignition sequence
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 F.68 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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