BoilerFaultCodesYour boiler has failed to light a flame, which means it has entered a lockout mode and stopped providing heating and hot water as a safety precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Ignition lockout. Possible solution/check: Gas present and at correct pressure, Combustion CO2 level, Flue condition, Ignition electrodes / harness / connections, Gas valve (coils 140-190Ω) / low voltage harness connection, Otherwise replace control board.
What causes this fault?
This fault happens because the boiler has tried to light a flame several times but failed to detect one. The most common reasons are a lack of gas reaching the burner, worn-out spark electrodes that can no longer create a spark, or a faulty gas valve that isn't opening properly.
This issue often crops up during the first cold snap of autumn when the boiler is worked hard for the first time after being idle all summer.
DIY fix possible
Check if your gas supply is active (e.g., check other gas appliances like a hob)Check if your gas meter has credit (if on a prepayment meter)Press and hold the flashing Reset button for five seconds to see if the boiler restarts
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 Blue light: Slow flash (normally off, flashes on), Lockout reset button: Flashing (reset required) — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch Greenstar 12i System is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.