BoilerFaultCodesYour boiler is lighting up but quickly switching itself off because it cannot confirm that a flame is safely present.
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, THEN GOES OUT. The flame is spreading across the whole burner, but not being detected.
What causes this fault?
This fault occurs when the boiler's control system fails to acknowledge that a flame has successfully lit, even if you can see it burning. The most common reason is a worn or dirty flame sense electrode that can no longer send an electrical signal back to the main computer to prove it is safe to keep the gas running.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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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