In the scene where Arnie takes Leigh home from the drive-in, he leaves Christine with the windshield wipers up. When he returns to Christine the wipers are down.
Good point but the car IS alive, man. Do you mean to tell me that you believe it can drive itself but you do not believe that it can operate its own wipers?
Again, the car is 'ALIVE' - eyes are the windows to the soul and all that. The windshield is the eyes of the car and the wipers are an attempt to resemble an actual characteristic of the eyes. Imagine this - watching the movie, your eyes are wide open - they leave and come back - your eyes are now narrowed, indicating anger. Maybe it's a stretch, but that's how I interpreted it.