BoilerFaultCodesWhat the manual says
Manufacturer manualIgnition fault, boiler fialed to light
What causes this fault?
This fault occurs when the boiler successfully lights but then loses its flame while it is supposed to be running. It is often caused by a dirty or worn-out sensor that can no longer 'see' the flame, or by an unstable gas supply that prevents the fire from staying lit. In some cases, internal debris or a failing control board can also interrupt the combustion process.
This fault can be more frequent during extreme cold spells if the external gas regulator is affected by the temperature or if a high demand for heating puts extra strain on older components.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Avoid the next call-out bill
A cover plan would handle faults like F4: no call-out fees, no surprise bills.
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