Most of the time it is airflow or rather the lack of it, that creates a demand for a lower temperature. Check out the aircon filter , the ducting, the vents etc. for blockage. See if the cabin is" airtight" in the sense that a window isn't creeping down while driving, check if the moonroof is properly closed etc The RX's aircon is pretty effective to keep the occupants cool in extreme hot climates and it shouldn't be necessary to add fans etc.
Last edited by nipponbird; 05-14-14 at 05:19 AM..