BoilerFaultCodesYour boiler is failing to light the flame properly, which means it cannot heat your radiators or 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.
What causes this fault?
This fault occurs when the boiler's control system attempts to start a flame but fails to detect one after several attempts. The most common reasons are a lack of gas reaching the burner, worn-out ignition sparks that can no longer bridge the gap, or a carbon-coated sensor that cannot 'see' the flame once it has lit.
This fault can be more frequent during the first cold snap of autumn when internal components that have sat idle all summer finally seize or fail under heavy use.
DIY fix possible
Check if your gas supply is turned on at the meterCheck if other gas appliances in your home are working correctlyPress the reset button (flame symbol with a cross) for one second
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 F.4 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Vaillant EcoMax Pro 18/28E 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.