It is the solar sensor for the electronic climate control - tells the brain how much sun is out there and adjusts the temperature accordingly.

Um, I think it adjusts the _blower_ speed accordingly; you yourself get to pick the temperature.

If strong sunlight is detected, it cranks up a higher speed for faster cooling, scaling the blower speed back as a temperature drop is detected by the inside temperature sensor (behind the little grille to the right of the cigar lighter).

The temperature is computer-controlled also! The system must compensate for your desired cabin temperature, and it can't do that with just the fan.

I have the same thing in my 96 and I don't have electronic climate control. It is not for the twilight sentinel as 94SSEgold has stated. The twilight sentinel is located in front of the steering wheel it is black and about the size of a quarter. What we are talking about here is in the very center of the dash and is a small black dome, smaller than a dime.

I always thought it was to do with the keyless entry, but I don't know why since the Keyless entry is RF not InfraRed.

Okay, I see what you mean...

I'm going to go back to the manual for another look...

Yes, that'* where the solar intensity sensor goes. Since you say you don't have the electronic controls for the A/C, I'm wondering whether you really have anything inside that, though...?

The dome over the sensor is actually a deeply translucent color that you can actually see through in strong light. If yours is definitely black, opaque, then I'd sayit might just be a filler (although I dunno why they wouldn't just put a flat plug in the hole).