Help with Gentex mirror wiring

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Believe it or not, my new Cadillac ATS didn't come with a self-dimming rear-view mirror. I got the "Standard" model and only Premium, Performance, and Luxury trims come with one. (Come on GM... it's an Cadillac for God's sake!)

Anyway, I snagged a Gentex mirror with HomeLink controls and compass display on eBay for only $100. The seller had it removed by the dealer upon taking delivery of a 2013 Hyandai in which he had a rear-view mirror with backup-camera installed. The mirror is a GNTX-536 / Model ZTVHL3 which I think must be an OE model because, although it looks identical, the similar aftermarket ones have different numbers. As such, I'm having a hard time finding a wiring diagram.

The harness is a 5-pin connector as shown below. I've installed Gentex mirrors before and am somewhat familar with their wiring. For example, I believe the gray wire (Pin 5), unused by the Hyandai from which the mirror came from, is a "Reverse" lead where other applications would connect a wire that it on/hot when the vehicle is in reverse and results in the self-dimming feature being disabled.

What I'm hoping for is your guys' knowledge/experience with helping me figure out the 3 wires that I need to connect. I believe one is for constant 12V which would power the HomeLink controls both when the vehicle is on/off. Another is for switched 12V which would power the self-dimming feature when the vehicle is on. And the third wire is for ground.



My guess is that Pin 1 - black wire on both sides - is Ground. That leaves Pins 3 and 4 - green and white wires on the mirror side - for constant and switched power. Experimentation to determine would be easy/harmless, but my guess is that the white wire (Pin 4) is constant power.

What do you guys think?

(Once I figure this out, then I just need to pull open the overhead console and see if I can find the appropriate wires to tap which will be another "research effort".)
 
With a multimeter, you could easily pull everything you need from the overhead console. I am sure there is a switched 12v for the Onstar buttons, and a constant for the maplights. I would probably be a little hesitant to tap into this though due to the fact that there is a network control bus that goes back to the BCM and controls all of these functions and a tap into the system might freak the BCM out.

I have installed these mirrors in previous vehicles, and I would run the wire down the A-pillar to the fuse box and tie it in with a temporary tap, and just put the ground wire under any nut I could easily find.

You could probably switch the Homelink also, so you just have to add one switched circuit (Homelink is switched in my Mercedes). There is also a wire to kill the auto dimming when the vehicle is in reverse, but you can disregard that connection if you like.

This is what you want, it's called add a circuit:

 
Wow. If this was a Cruze, I can understand but I'm very surprised a Cadillac - regardless of entry level or not - did not come with this.

Based on my experience installing these, I would imagine it would be something like this:

Black: Ground
White: 12V source (ignition on)
Green: 12V source (constant)

If there is a grey or black/white striped wire in there, that would be for the reverse disable feature you mentioned.
 
Originally Posted By: Falcon_LS
Wow. If this was a Cruze, I can understand but I'm very surprised a Cadillac - regardless of entry level or not - did not come with this.



It's not standard in an entry level 3 series either, but it should be.
 
Originally Posted By: dishdude
It's not standard in an entry level 3 series either, but it should be.


True. Lexus tends to shine with things like this.
 
I remember when I installed one of these a while back on when I used to service an Audi A6, I opened up the mirror and I believe the leads were abbreviated with their function where they met on the circuit board. Not sure if this is the case here. Or I could just be remembering the diagram listed by the person I bought it off of on ebay.

I'd say if your trim was available with the mirror as a dealer option, chances are likely that there is a harness plug already up there. But I've also seen the dealer installed ones which have you run wires down the pillars.
 
Originally Posted By: ChrisW
I'd say if your trim was available with the mirror as a dealer option, chances are likely that there is a harness plug already up there.

That's what I was hoping for, but I've been told by another ATS owner in a Cadillac forum that it's not the case. But I haven't looked myself.
 
OP Update: I finally got around to installing the mirror this weekend. From the fuse box on the side of the dash on the driver's side, I used one add-a-circuit to tap switched power and another to tap constant power. Those were connected to two conductors in a four-conductor wire and I grounded a third wire. I was then able to run the wire behind the A-pillar trim and tuck it under the headliner where it meets the windshield. If you look back at the picture in my original post, Pin 1 was ground, Pin 3 was constant power for HomeLink, and Pin 4 was switched power for the Compass and auto-dimming feature.

The installation worked out great and looks like it came from the factory with the mirror. Though, it's actually a nicer mirror... one of the newer Gentex models where the whole surface is mirrored/reflective rather than having that black spot with the readout.
 
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