Technical description
Defective gas–valve closure mechanism | Cause: Leak in gas valve assembly, electronic fault
What causes this fault?
This fault occurs when the boiler detects that gas is still flowing or the valve hasn't shut properly after the flame should have gone out. The most common reason is a physical internal leak within the gas valve assembly or a communication failure where the main control board incorrectly reads the valve's position.
Engineer required
This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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