mdknapp

All,

I posted a message a few months ago about my '99 A6 Avant. The car had been in an accident and whoever fixed it replaced one of the Halogen headlights with a Xenon. Thinking that the car originally had Xenons, I replaced the second headlight with a Xenon. When I replaced the headlight, I noticed that the wires that aim the headlights were missing..

A few weeks ago, we went hiking with 5 people and all of our backpacks.. On the way there, every car was flashing us because the Xenons were too high with all the weight in the car. Luckily I had an allen wrench and was able to reaim the headlights.

So anyway, over the weekend I started looking at the headlight assembly. I took apart the Xenon aiming control. I originally thought that the headlight aiming must be controlled by pulse width modulation or a similar scheme.. This turned out not to be the case - it is actually much easier than that.

The IC inside the aiming control was covered in paint by Hella so I couldn't see what the part number was. This came off with nail polish remover. It turns out that the part in the headlight is a Philips TDA3629... The datasheet for this part is on Philips website, here:
http://www.semiconductors.philips.com/pip/TDA3629_N2.html

According to the datasheet, there are just three connections needed to operate the headlight aiming: Power, Ground, Adjust. All the adjust signal needs is an analog voltage between ground and Vbat.. Which can be done with ONLY a potentiometer! So I traced the connections back from the Philips IC.. Inside the Xenon headlight assembly, the wires are as follows:

Blue: Bat. Positive
Orange: Aim adjust
Pink: Bat. Negative

So I hooked up the pot which I ripped out of an old wall dimmer switch from my house. And it worked! I can aim the headlight by turning the pot... The TDA3629 does all of the positioning work... the headlights will always go to the same spot depending on how the pot is set.

Note that in the TDA3629 datasheet, it says that the purpose of the part is to allow the driver to control the headlight aiming from a potentiometer on the dashboard... Interesting, since it is usually controlled by the Xenon aiming computer, right? I did a little investigation, and it turns out that at least in Germany, on at least in some Audis, the headlight aiming IS on the dashboard.. It is not computerized. The control is located next to the dashboard dimmer by the headlight switch (ever wonder what that empty location is for?)..

So anyway, I have a question... Does anyone know a good way to run wires from the headlights back into the cabin? Is there a way to do it without drilling?

I will post pics as this project progresses.

Thanks
Mike

Egil A64.2s - S6

according to our government!

4Driver4

Ever take a good look at some of the folks driving around?

saabSean

Because I think that would just be cool as hell.

BTW, we had a discussion on here recently that the automatic xenon aiming potentiometers are actually contained inside the wheel wells, attached to the front and rear suspension on the left side. I wonder if the location switches to the right side for right hand drive? Hmmm.

ArtsA6Q

I had meant to take some time to explore the system myself. It appears that the autoleveling actuator is mounted inside of the headlight assembly. There are three wires that connect to it. I was going to apply power/ground in various combinations to see if I could get the adjuster to move. But you did all the work for me.

As for the wiring, I have already figured that out. There is a rubber boot covering a network of cables and lines that travel through the firewall. It is located underneath the cabin air filter. If you cut the boot carefully on the underside or in some other strategic location, you can easily fish some wires through it. You have to remove the glovebox (it comes out as an entire assembly, with three bolts IIRC) in order to expose the other side. I have my power wire for my subs going through the same location and have not had any problems. I used a bit of lubricant to fish the wire through.

It would be nice to see a writeup of all the connections with diagrams. We could then vote to have it posted in Stoney's FAQ pending his approval.

Question: Does the autolevel mechanism adjust the low beams only or both high and low as a whole? Looks like it adjusts the whole reflector unit, but I could be wrong.

Niro

one of the existing holes that wiring harness is going through. Usually there are rubber grommets that seal. Push the wires through one of them; the grommet should stretch and accommodate your cables.

mdknapp

I belive that it adjusts both high & low beams.. But the high beams are so unfocused that it seems like it wouldn't make a whole lot of difference. As Audisean says, it would be extremely cool to have the German switch like this one on ebay.de:

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&category=53948&item =7934724934&rd=1

Apparently this guy only ships to Germany though so you'd need to have a connection there

It is SO cool to watch the headlights move when you adjust the dial! I'll post a full report when I'm finished and maybe it will be worthy of Stoney's FAQ.

-Mike

ArtsA6Q

=)

eh?6Q

Shoestring bi-xenon! Hi-beams triggers a relay to change resistance and adjust beams up 10degrees !

mdknapp

But maybe it would work?!