BoilerFaultCodesWhat the manual says
Manufacturer manualBurner in fault position. Flame signal is already present at burner start. Check the ionisation electrode and lead.
What causes this fault?
This fault occurs when the boiler's sensors detect a flame signal before the ignition sequence has even started. The most common reason is a build-up of carbon or moisture on the sensing probe which sends a false electrical signal to the control board, or a faulty internal component that incorrectly thinks the gas is already burning.
This issue is more frequent during periods of high humidity or heavy rain, as moisture ingress can affect the electrical signals on the ignition leads.
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 F3: no call-out fees, no surprise bills.
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