I have a 2005 FX4 and I can't figure out what the black box attached to the rear-view mirror is for. My mirror is just a plain mirror, but the black box has a 4-cond cable that plugs into and the cable goes up into the headliner. Any idea? I'm thinking it was installed by the CIA as part of the Patriot Act to keep track of my every move.

 

I believe it is for the compass.

 

its your light sensor when it gets dark it turn on your automatic lights.

 

...and auto dimmer for the rear-view mirror to keep headlights from blinding you.

 

Guys guys its the sensor module for the factory compass. The little red blinking light on the dash top is the light sensor for the auto headlights. The sensor for the auto dimming mirror is the small circle on the rearview mirror facing the driver (and also facing the rear of the vehicle).

 

mine has remote start, there's a black box next to my mirror for that.

 

And the winner is.........compass. When I disconnect the box the instrument cluster compass reading goes blank.

Thanks to all.

 

the light is for the theft deterrent

 

The red light is a anti theft deterrent, but also with in the black bubble there is a sensor to turn the automatic headlights on. If your truck is equiped with the auto headlights, stick your hand over top of the black bubble and red light and with in a few seconds your headlights will turn on.

Like SAJEFFC said the hockey puck looking thing on the mirror is for the compass, and there is a small photo cell just under the mirror that is for the auto dimmer mirror that faces the back of the truck to sense headlights behind you, and there is also one on the back of the mirror (facing the front of the truck) that determines the brightness outside.

 

 

Congrats jeff, nice to see you get something right!

 

I know right?? I screwed up on that tire pressure thingie in the spare post! :o

 

yeah i figured out the mirror thing when i first got the truck. it was weird at first and i when i put two fingertips over the photocells, the mirror faded back to normal. didn't know about the auto headlight thing though.

 

yeah its the compass and the little button on top of it is to reset the compass and calibrate it...if you hold it down it will bring up the zone and then hit it again and it will bring up the calibration...same thing as holding down the reset and setup buttons...i know nobody asked but incase anyone was wondering..

 

Does someone know for sure that the automatic headlight sensor is in the blinking light housing on the dash?