i have a disco2 2002 and it has air con.it is seated in the middle of the dash in between the front two air vents i found out that it was a sunlight sensor and that got me thinking what the hell does it do.
Detects the angle and intensity of sunlight and provides info to air con. If sun is high and bright it prempts the solar gain and boosts the air con to compensate.
...And can also adjust the left/right climate control balance on top of your manual settings. I.e. If it's sunny on the passenger side but in shadow on the drivers side, it can make the passenger side cooler even though you may have the same temp set for both sides.
