High Lockout
SUP on Grant Vortex

Your boiler's temperature sensor has stopped sending the correct signals, meaning the system doesn't know how hot the water is and has shut down as a precaution.

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

Supply sensor short / Supply sensor open

What causes this fault?

This fault occurs when the main sensor responsible for monitoring the temperature of the water leaving the boiler fails or loses its connection. The most common reason is that the internal thermistor has worn out through constant heating cycles, though it can also be caused by moisture corroding the sensor's electrical pins or a loose wire in the internal harness.

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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