High Lockout
9L on Ideal Maximiser SE

Your boiler has stopped working because of an internal communication error between the main control board and the gas valve.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Improper electrical connection of gas control combination or defective control panel.

What causes this fault?

This fault occurs when the boiler's main computer loses the ability to talk to the gas valve, which is the component that controls fuel flow. The most common reason is an electrical glitch in the circuit board or a loose connection in the wiring that prevents these two parts from synchronising safely.

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.

Find a Gas Safe engineer
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