BoilerFaultCodesWhat the manual says
Manufacturer manualBurner in fault state. No flame signal is present. Cause: Check the ionisation electrode and leads, measure the ionisation current, check the gas pressure, check the gas combination valve, ignition, ignition module, ignition electrodes and the condensate drain. Press E.
What causes this fault?
This fault occurs when the boiler's internal computer tries to start the burner but cannot detect a flame after several attempts. The most common reasons are a dirty or worn-out sensor that can no longer 'see' the flame, or a physical blockage in the gas supply or drainage system preventing ignition. Because the boiler cannot confirm it is burning fuel safely, it shuts down completely to prevent gas from building up.
This fault is more common during freezing winter temperatures, as a blocked or frozen condensate drainage pipe can back up and prevent the boiler from lighting.
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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