High Lockout
F6 on Glow-worm 30ci Plus

Your boiler has stopped working because a sensor that monitors the temperature of the water leaving the unit has failed or has a loose connection.

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

Central heating flow NTC fault

What causes this fault?

This fault occurs when the boiler's internal computer can no longer read the temperature of the water being sent to your radiators. The most common reason is that the flow thermistor has physically degraded over time or developed an electrical short, though it can also be caused by a vibrating or loose wiring connection inside the unit.

This fault often appears when the heating is first turned on after summer, as the sudden change in temperature can push a struggling sensor to total failure.

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

F1View →F2View →F5View →

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