This thread is especially addressed to those of you who own a (base line) 2001-2003 A4 and want to retrofit a rear view mirror with the auto-dimming function, since many of these cars did not come with it from the factory. Although this was previously covered (quite well actually) by other members, I assume that after reading all the threads and comments, sooner or later you'll find yourself sitting in the car with your new (to you :) mirror, trying to figure out a way to make it work; since yours does not have a connector for this purpose and the wiring harness is totally different than anybody else's. From the very beginning I want you to know that although it seems like a big hassle from a perspective or another, that's really not the case... you know, just try not to loose all that excitement quite yet :)
Tools / Parts needed:
* Rear View Mirror (with Auto-Dimming & Compass) - Part NO: 8E0 857 511 4PK (please note the German spelled "KOMPASS" as it's the only way to tell if it has the compass or not)
* 6 Pin Connector from a donor harness (this is a MUST !)
* Cutting Pliers
* Electrical Tape - I used cloth tape since it offers more flexibility and looks OEM
* Butt Connectors - or self-soldering heat-shrink tubing in my case (that's what the torch lighter's for :)
* Flashlight
* Multimeter
* Cutter / Scissors
* Wire Stripper
* Phillips-Head Screwdriver
* Small Flat-Head Screwdriver
Step 1: Dome Light/Mirror Removal
Use the small Flat-Head screwdriver to gently pry the clear plastic cover. It has two hook type clips towards the front. Next remove the plastic trim that sits in the front of it (the one that contains the map light covers) by prying the left and right corners. Once removed, you'll find two Phillips-Head screws in between the small light bulbs for the map lights. Now remove the whole assembly starting from the front as well as the 12 pin connector that comes to it. If you take a closer look where it was plugged in, you'll notice that all 12 pins are present... just keep that in mind and set it aside for now. Next, grab the mirror from the holder that sits on the windshield and twist it to the left about 45 degrees. Done !
Step 2: Understanding The Pinout
Now, first thing while looking at the 12 pin connector would be to take the shell off of it so it'd give you access to the actual pins. (it just slides to one side) What you primary need is a constant Ground (Brown) and a switched +12V. This is where I got confused too, since on every thread and post others would say that Pin 4 and Pin 7 are missing. In my case the missing pins were Pin 1 and Pin 12 and Pin 7 (Black) was actually the live wire I was looking for... so at this step it'd be good to use a multimeter and test this yourself since the harness is different from car to car. Although, here's what I found after burning my head with hours and hours of looking over diagrams:
1 - Auto-Dimming inhibitor signal (sends Ground)
2 - +12V for the red backlight LEDs
3 - +12V for the bulbs (10A)
4 - ?
5 - Ground from central locking
6 - Constant Ground
7 - +12V ignition switched
8 -> 12 rear reading lights signal pass-through
On the 6 Pin mirror connector you're mainly interested in Pin 1 (Live) and Pin 2 (Ground)... however I wanted to wire in Pin 6 which turns the auto-dimming function off while interior lights are on. So I had to add the missing Pin 1 to my dome light harness and connect it to Pin 6 on the mirror harness. I used one of the pins that I just pulled out from the mirror connector... just a bit of soldering magic later and yeah; problem solved ! This is how I did it (left side - mirror connector / right side dome light connector):
Pin 1 - Pin 7
Pin 2 - Pin 6
Pin 6 - Pin 1
Step 3: Making The Connection
At this point you have to fish out the mirror connector through the front of the headliner. You'll be able to feel a small gap that was factory designed for the wires to pass through. Now use whatever you want to make a strong connection and a good contact between the three wires. As a personal preference I wrapped everything in cloth tape to make it look a little bit more like 'done from the factory'. (I also cleaned the main light assembly, polished all the transparent pieces and replaced the 4 bulbs since I had a better chance.)
Step 4: Putting Everything Back Together
Start with the mirror. Push in the little felt piece that goes against the windshield. Set the mirror in it's position and twist it 45 degrees to the right until you hear a solid click. Push the connector in until it clicks and clip it back into the two small plastic tabs to secure it in place. Now close everything with the other half of the trim piece and that is that. Try it to see if everything works before putting the light assembly back it. Enjoy !
Thanks to everyone who made this possible, especially to a person from this wonderful community who shipped this half-way across the world just so I can look at that little compass each ride from now on...
(one of the few, if not the only one in EU... since here NO car has the compass in the mirror)
"Dani"
Reply With Quote
Originally Posted by Gunnarrrrr
If you insist...
Bookmarks