BoilerFaultCodesYour boiler's control board is receiving an incorrect electrical signal from the flame sensor, meaning it cannot safely confirm if the burner is lit.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flame input signal out of range (0 or 5V)
What causes this fault?
This fault occurs when the boiler's main control board receives an impossible electrical signal from the flame sensing system, often due to a permanent short circuit or a component failure. The most common reason is an internal electronic fault within the main circuit board itself, though damaged wiring or a degraded sensing probe can also trigger the error. Because the boiler cannot accurately detect if a flame is present, it shuts down immediately to prevent unsafe operation.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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