Where is the GEM located for the windshield wipers and dome light on a 1997 F-150 extended cab?

Some vehicles are equipped with automatic rain sensing wipers. They have a light sensor that aims at the windshield below the mirror. If the glass is wet part of the light reflect/refracts back and the wipers will come on.Some vehicles are equipped with automatic rain sensing wipers. They have a light sensor that aims at the windshield below the mirror. If the glass is wet part of the light reflect/refracts back and the wipers will come on.

Dryness will cause the wipers to vibrate or jitter against the glass. If there is not enough moisture on the windshield (for example, a light sprinkle of rain) the wipers may move with a jerky motion. Also, the wipers could be very old, and the wiping rubber/vinyl could have lost some of its softness and flexibility. If you mean vibration when they are not active, the wind against the windshield could cause them to flutter if they are not properly seated. A clean windshield and new wiper blades will usually cure the vibration.

You have automatic rain sensing wipers and this is the sensor for the rain. If you turn the wipers all the way off or on, the light goes out.

If it is the light in the gauge console, it is to let you know the headlights are on automatically. Like when the windshield wipers are on, or that its dark enough to have them turn on.

Many newer cars have automatic windshield wipers. These work with a rain sensor, usually mounted near the rear view mirror. The sensor uses infrared light to sense moisture- droplets scatter light, and the when enough light is scattered, the sensor decides that it's raining. It then signals for the wipers to come on. Dirt can also fool the sensor into turning the wipers on.