High Lockout
F7 on Glow-worm Xtramax HE

Your boiler is having trouble measuring the temperature of your hot water, which means it cannot safely heat water for your taps.

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

Domestic Hot Water thermistor fault.

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring your hot water temperature fails or sends an unreadable signal to the control board. The most common reason is that the sensor has suffered electrical failure due to age, or the wiring connecting it to the main system has become loose or damaged.

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.

Find a Gas Safe engineer
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Related fault codes

F1View →F14View →

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