That is the sunlight sensor.
It gives input to the Automatic Climate Control system. When it senses sunlight coming into the car it cranks up the A/C a bit to help you keep the car cool.
By the way, it should have a little smoked plastic cap on it. That cap is not removeable. If it gets broken off, you will start to get clicking noises from behind your dash as your A/C system struggles to maintain a set temperature. Its an annoying little thing when it happens.
Well, the A/C system controller is calibrated to get info from that sensor with the smoked cover in place. You would need to cover it with something that transmits the same amount of light as the original (or at least close to it) for it to work properly. If you can find something that will stay in place, give it a try and let us know how it works out. You are not the only person this has happened to....
Replacing it is easy if the dash is out. :wink: It needs to be removed/inserted from the bottom side of the dash. Not sure if it can be done with the dash still in the car because you probably can't get your hand up there.
The ambient daylight sensor is impossible to remove when the dash is in the car. The blower fan housing, the body reinforcement bar (the huge metal bar that goes across the dash that you see when you remove the upper dash pad), along w/ the fact that you have to unscrew the plastic ring that secure's the sensor to the dash, THEN you have to unplug the wire connector before you can remove it (and that wire does not have much slack in it). Don't see how it can be done w/ the dash in place. That sensor is usually the last thing I have to undo before the dash pad can be removed out of the car.
The sensor can be removed while the dash is still installed, only you have to remove everything down below. It also helps to be mid summer, 90+ degrees if possible, a nice and thick humidity, itchy weeds and a blaring sun to help produce the needed "sweat lube" to assist your arm as it snakes around all those little gizmos behind the dash. Don't forget to grimace and grit your teeth as your arm is poked and proded by all sorts of comforting points and protrusions.....a hidden wasp nest always helps too!