High Lockout
F00 on Glow-worm Flexicom hx

Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the 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

Flow NTC fault

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring the heat of the water leaving the boiler fails to send a reliable signal to the main control board. The most common reason is that the sensor has physically degraded or developed an electrical short, meaning the boiler shuts down as a safety precaution because it no longer knows if the water is at a safe temperature.

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

F01View →F10View →F11View →

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