High Lockout
Neon1 on Glow-worm Ultimate

Your boiler has lost power because of an electrical issue or a blown fuse inside the control unit.

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

Fault with mains supply or PCB fuse

What causes this fault?

This fault occurs when the boiler's internal computer loses electrical power, preventing the system from starting up at all. The most common reason is a blown fuse on the circuit board, which often happens due to an unexpected power surge or a failing internal component causing an electrical short.

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

Neon 2View →Neon 3View →

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