BoilerFaultCodesYour boiler is failing to light the gas flame required 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: No flame during start-up.
What causes this fault?
This fault occurs when the boiler's control system attempts to start the combustion process but cannot detect a stable flame. The most common reasons are a lack of gas supply to the unit, a worn-out ignition spark, or a build-up of carbon on the internal probes that monitor the fire. Without a confirmed flame, the boiler stops for safety reasons to prevent unburnt gas from entering the system.
This fault can occur more frequently during the first cold snap of autumn when internal components that have been dormant all summer are suddenly required to work under high load.
DIY fix possible
Check if other gas appliances, like a cooker, are working to confirm gas supply is active.If you have a prepayment meter, check that there is enough credit.Ensure the condensate pipe (the plastic pipe outside) hasn't frozen in cold weather.Try resetting the boiler by pressing the reset button for a few 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 F004 — 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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