BoilerFaultCodesYour boiler is successfully igniting, but it cannot detect the flame and shuts down immediately 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, THEN GOES OUT.
What causes this fault?
This fault occurs when the boiler's safety system fails to confirm that a flame is present even though the burner has physically lit. The most common reason is a buildup of carbon soot on the sensing probe or a loose connection in the wiring that transmits the 'flame detected' signal back to the main control board.
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.
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A boiler cover plan would cover faults like F4 — no call-out fees, no surprises.
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