i believe i've read from i think old guy or diagnosicator mentioned in another posted that the HVAC sensor is in the tiny grill's in the HVAC unit itself. the small rectangular bubble on the dash center grill was a UV light sensor for MY2002's which was replaced by the auto headlight sensor in later years. the UV light sensor controls the auto vent direction which i really really miss as the 2004 model doesn't do this as well as the 2002. I'd almost trade someone my car just to have the better automatic vent direction function.

i could be wrong though...