High Lockout
20 on Glow-worm Xtramax HE

Your boiler is having trouble sending signals between its internal electrical parts, which is preventing it from working correctly.

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

COMMUNICATION FAULT: THIS FAULT MAY BE OCCASIONAL AND CAUSED BY ELECTROMAGNETIC INTERFERENCE, OTHERWISE CHECK THE MAIN CONTROL BOARD (PCB).

What causes this fault?

This fault occurs when the 'brain' of the boiler loses contact with its internal electrical components, meaning it can no longer send or receive instructions. It is usually caused by a loose connection in the wiring or a hardware failure within the main control board itself. Occasionally, outside electrical interference from other household appliances can disrupt these signals and trigger the 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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