High Lockout
05 on Glow-worm Ci Range

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

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

Overheat fault

What causes this fault?

This fault occurs when the water inside the boiler reaches an unsafe temperature, triggering a safety sensor to cut the power. The most common reasons are a pump failure that stops water from moving or a blockage in the heat exchanger that traps heat inside the unit.

This issue is more frequent when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.

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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