High Lockout
9H on Ideal Maximiser SE

Your boiler's internal computer has suffered a technical failure and cannot communicate 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

Internal failure control panel.

What causes this fault?

This fault occurs when the boiler's central brain suffers a critical hardware failure or a communication breakdown between the internal components. It is often caused by an electrical surge, moisture ingress, or simply the natural degradation of the solder joints on the circuit board over time. Because the computer can no longer send instructions to the burner or pump, the boiler shuts down as a safety precaution.

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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