Boiler Ignition Failure — Not Lighting
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →If you smell gas at any point, stop immediately. Turn off the gas at the ECV, ventilate the room, and call National Gas Emergency on 0800 111 999. Do not attempt to reset a boiler if you smell gas.
Ignition failure is one of the most common boiler faults — the boiler sparks, attempts to light, fails, and locks out. The cause is usually a dirty or faulty ignition electrode, a gas supply problem, or a faulty gas valve. Some checks are DIY-safe; actual repairs must be done by a Gas Safe engineer.
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Most likely cause & what to check
Try resetting the boiler by pressing the reset button (usually red or marked with a flame symbol). Hold for 3–5 seconds and release. Many ignition failures are one-off events — a single reset often resolves them.
Check that other gas appliances (cooker, gas fire) are working. If they are not, your gas supply has been interrupted — check whether a gas meter credit has expired (prepayment meters), or call your gas supplier.
Check the boiler pressure gauge — if below 0.5 bar, the boiler may fail to light as a safety measure. Repressurise to 1.5 bar using the filling loop.
If the boiler sparks (you can hear clicking) but will not light, the ignition is working but gas is not reaching the burner. Possible causes: gas valve fault, or air in the gas supply. Only reset the boiler 2–3 times maximum — a Gas Safe engineer is needed if it keeps locking out.
If there is no clicking at all (no spark attempt), the ignition electrode or its lead has failed, or the control board is not detecting the electrode. This requires a Gas Safe engineer to test and replace components.
Note the fault code displayed on the boiler — look it up on plumbingadvice.co.uk/boiler-fault-codes to understand exactly what the boiler detected before locking out. This helps an engineer diagnose quickly.
Typical repair costs: ignition electrode replacement £80–180; gas valve replacement £200–350; control PCB replacement £200–400.
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