BoilerFaultCodesYour boiler is unable to safely light the flame needed to provide heating and hot water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Ignition fault, boiler failed to light
What causes this fault?
This fault occurs when the boiler attempts to ignite several times but fails to establish or detect a steady flame. It is often caused by a lack of gas reaching the burner, worn-out spark electrodes, or a faulty sensor that cannot confirm the flame is safely lit.
This fault is more common during extreme cold snaps, as freezing temperatures can cause external gas regulators to stick or thin pipes to become restricted.
DIY fix possible
Check that your gas prepayment meter has credit (if applicable)Verify that other gas appliances, such as a hob, are working correctlyPress and hold the reset button (flame symbol with a cross) for five seconds
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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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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