Hi , its my first post on this board. Sorry to appear so dumb with this question: I've just stumble on an '85 (maybe '87) Firebird that have strange control/led on the interior view mirror. The mirror/control panel is part of the mirror (not an addon) Just below the mirror on the right you have an sliding on/off switch, a little red round led and on the left a rotary switch (potentiometer) with some writing on it: it begin with the word near, 1-2-3-4-5 etc and end with Far. At the back of the mirror/control panel, looks like a little hole with some kind of "captor". And a 3 wire connector.

When I dismantled the headliner, I saw a black wire fixed with a screw in the sheetmetal (ground) ,then two other wire, a red/green wire and a all green wire that run on the A pillar, the red/green is connected on the fuse box in a location named "ING", maybe the positive ignition activated. The all green is spliced together with another same green wire that came from a double black connector hiden behind the carpet were your left foot rest. It look like the wire from the cruise control module (the little black plastic box located under the passenger side dash behind the map pocket). But I'm no sure.

My questions are: Is it a factory option? does it belong to the cruise control option? Is it to disable cruise control activities when a car is to near up front? or maybe some kind of radar detector?

And if it's for the cruise control, does it work with any of the third gen cruise control module?

Thanks!

 

That mirror is a self-dimming mirror. You can set the sensitivity with the rotary switch. At night, when someone gets close their headlights hit the sensor and the mirror auto-flips to dim. When the lights go away, it flips back.

 

...but two questions remain (or pop up)...why this green wire? If its a auto dim mirror, why it need this green wire? red and black for power look to be enough for this kind of circuit but this intriguing green wire, where it goes?? its use?

Also since the sensor is in the back case of the mirror pointing forward (looking outside the front of the car because it dont have the familiar black dot on the reflective surface of the mirror itself), how can this work (it's for the car that follow you not the one coming in front of you) ? the mirror will auto dim each time you cross another car (that goes the other way)..

 

Gunner is correct: The mirror (an option) is auto-dimming. IIRC, the green wire disables the auto-dimming function when the vehicle is put in reverse. Try a and you find more info.

JamesC

 

I've done some seach but I havent found yet anything (here and on the net) . And to be sure I need a picture to compare when I found info.

I finally found one for sale on Ebay with a picture.Look exactly the one I've found.

I'm still surprised of this third wire and the weird sensor orientation, since other model of auto-dim mirror have only two wire and the sensor in the right direction.

It's a shame that it was not a "cruise control following distance sensor"...I was dreaming ....it will be cool to have this kind of gimmick to help cruise at the same speed as the preceeding vehicule
Thanks for the info you gave me . Very appreciated

 

that sounds like it would be for dimming the high beams on your car when a car is coming at you. then turning the brights back on after the car has passed.

 

JamesC is right..this green wire is for disabling the dim effect qhen the car is in reverse.