High
F6 on Heatline Capriz 25 System

Your boiler is unable to read the temperature correctly because a sensor on the outside of the system is disconnected or faulty, which has caused the boiler to shut down for safety.

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

External NTC thermistor fault

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

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