BoilerFaultCodesYour boiler is unable to light the gas to produce heat, meaning your heating and hot water will not work.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Start-up failure: Ignit. unsuccessful - Failure during start-up or ignition unsuccessful. Gas pressure monitor or thermal cut-out has been triggered.
What causes this fault?
This fault occurs when the boiler attempts to ignite three times but fails to establish a steady flame. The most common reasons include an interrupted gas supply, a worn-out ignition spark plug, or a component failure that prevents the gas valve from opening correctly.
This fault is more frequent during extreme cold snaps, as external gas meters or regulators can sometimes freeze, restricting the flow of gas to the property.
DIY fix possible
Check if your gas meter has credit (if using a pre-payment meter).Ensure your emergency gas lever or external gas valves are fully open.Restart the boiler by pressing the reset button (the 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.28 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.