High Lockout
F11 on Glow-worm Xtramax HE

Your boiler's internal computer parts are struggling to talk to each other, preventing the system from starting up.

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

Electronic control board (PCB) communication error.

What causes this fault?

This fault occurs when the main electronic brain of your boiler loses its connection with the internal components it needs to control. It is usually caused by a physical break in the wiring or a burnout of the circuitry on the printed circuit board itself, preventing the boiler from receiving the signal to start heating.

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

F12View →F13View →

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