BoilerFaultCodesWhat the manual says
Manufacturer manualFault: Flame signal unstable - Flame monitor reports an unstable flame signal
Shared across the range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s manual.
What causes this fault?
This fault occurs when the boiler's control system cannot detect a consistent, healthy flame after the burner has ignited. The most common reasons are a worn-out sensing probe that can no longer 'see' the flame, or a gas valve that isn't delivering a steady flow of fuel to keep the burner lit.
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.
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