High Lockout
OPn on Grant Vortex

Your boiler has detected that a temperature sensor cable has disconnected or become faulty, preventing the system from monitoring water flow correctly.

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

HP flow sensor open / HP return sensor open

What causes this fault?

This fault occurs when the boiler's control board loses communication with the sensors that monitor the temperature of the water entering or leaving the unit. It is usually caused by a sensor internal failure, a loose connection, or damage to the wiring harness that prevents the electrical signal from reaching the main controller.

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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