BoilerFaultCodesYour boiler is detecting a flame when there shouldn't be one, so it has shut down for safety purposes to prevent a malfunction.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Burner in fault position. Flame signal is already present at burner start. Check the ionisation electrode and lead.
What causes this fault?
This fault occurs when the boiler's sensors detect a flame signal before the ignition sequence has even started. The most common reason is a build-up of carbon or moisture on the sensing probe which sends a false electrical signal to the control board, or a faulty internal component that incorrectly thinks the gas is already burning.
This issue is more frequent during periods of high humidity or heavy rain, as moisture ingress can affect the electrical signals on the ignition leads.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like F3 — no call-out fees, no surprises.
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Could it be time for a new boiler?
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