It measures the temperature inside the car for the ACC. When the convertible top is not open, the controller compares this value to the temperature selected by the passenger to regulate the temperature of the air passing through the air vents. When the top is open, the controller disregards the sensor and assumes a constant temperature of about 72 degrees.

If the sensor is disconnected, the controller will recognize this. I don't know, but I will guess that it would operate as if the the top were open.