High Lockout
E09 on Keston C36

Your boiler has detected an internal communication problem between its electronic brain and the gas supply system, meaning it cannot safely light the flame.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Valve drive error - possible gas valve or control box fault.

What causes this fault?

This fault occurs when the boiler's main control board loses the ability to communicate with or operate the gas valve safely. The most common reason is an electrical failure within the gas valve's motor or a fault on the circuit board that prevents it from sending the correct starting signal. In some cases, it can be caused by loose or damaged wiring connections between these two vital components.

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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