High Lockout
F13 on Glow-worm Flexicom sx

Your boiler has lost communication with the temperature sensor on your hot water cylinder, meaning it cannot tell how hot your water is.

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

Tank NTC fault

What causes this fault?

This fault occurs when the boiler can no longer receive an electrical signal from the temperature probe attached to your hot water tank. The most common cause is a failure of the sensor's internal components or a loose connection in the wiring that links the cylinder to the boiler's main control board.

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 →F11View →F22View →

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