High Lockout
16 on Glow-worm EnergySaver Combi

Your boiler's main internal computer has developed a software or hardware failure and can no longer control the heating and hot water.

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

There is an internal fault in the Automatic Control Module.

What causes this fault?

This fault occurs when the boiler's main control board experiences a critical internal communication failure or a physical burnout of its circuitry. It is often caused by long-term heat exposure degrading the electronic components or a sudden electrical surge that damages the board's memory chip.

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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Related fault codes

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