High Lockout
13 on Glow-worm Xtrafast 120

Your boiler's internal computer has developed a fault and can no longer control the system safely.

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

Main PCB fault

What causes this fault?

This fault occurs when the main control board's internal memory or processor fails, meaning it can no longer communicate with the boiler's sensors or valves. The most common reason is electrical fatigue or a power surge that has damaged the delicate circuitry on the board. Over time, heat exposure within the boiler casing can also cause the soldered connections on the PCB to degrade and fail.

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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