High Lockout
9A on Ideal Maximiser SE

Your boiler's main internal computer has developed a fault and is no longer communicating correctly with the rest of the system.

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

Defective control panel.

What causes this fault?

This fault occurs when the boiler's central control board suffers an internal electronic failure, preventing it from sending commands to the burner or pump. It is usually caused by aging components on the circuit board or a sudden electrical surge that damages the sensitive microprocessors. In some cases, loose wiring connections between the interface and the main board can also trigger this error.

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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