Brdman*

<ul><li><a href="http://www.wikihow.com/Remove-and-Replace-the-Heater-Core-(Matrix)-in-a-'92-'98-Audi-C4-(100/A6/-S4/S6-)">http://www.wikihow.com/Remove-and-Replace-the-Heater-Core-(Matrix)-in-a-'92-'98-Audi-C4-(100/A6/-S4/S6-)</a</li></ul>

berlina

<ul><li><a href="https://forums.audiworld.com/a6100/msgs/50098.phtml">click here for original writeup</a></li></ul>

Seattle Scott

<ul><li><a href="https://forums.audiworld.com/a6100/msgs/61650.phtml">Pain in the ***</a></li></ul>

rmccomiskie

The Osram 2721MF (1.2W) is available at www.autohausaz.com here:
1988 Mercedes &gt; 300E &gt; Body, Trim &amp; Lighting &gt; Instrument Light &gt; 2721MF

$0.78 each (5/30/08).

The 2W Osram 2722MF bulb is $0.93, OEM PN:893919040A, green base.

rmccomiskie

Here's what I did ('97 A6):

Follow directions in the FAQ to remove the instrument cluster from the dash.
<img src="http://pictureposter.audiworld.com/56914/remove_shift_display.jpg">
Pull the electrical connector. Use a Phillips screwdriver to remove the shift display module from the instrument cluster. It should slide out easily.
<img src="http://pictureposter.audiworld.com/56914/remove_shift_indicator_cover.jpg">
Use a Torx T-8 bit to remove the screws from the module cover.
<img src="http://pictureposter.audiworld.com/56914/remove_PCB.jpg">
Remove the printed circuit board from the module. I pried the tab on one end until it cleared the slot then worked the other end free. A word of caution, make a note of the orientation of the board in the module. It is possible to reinstall it the wrong way.

Now the hard part. Remove the lamps from the board. The trick is to desolder the wires, pull the lamp and keep the holes clear of solder.

I found that the easiest way is to break the bulbs. I squeezed each bulb with needlenose pliers until they shattered leaving 2 separate wires. Be sure to wear eye protection.
<img src="http://pictureposter.audiworld.com/56914/hang_vise_grips_from_lamp_wire.jpg">
Then I hung small vise grips from each wire while I heated the solder on the other side. When the solder melted, the weight of the vise grips pulled the wire through. Of course the hole closed up with solder. Not good.
<img src="http://pictureposter.audiworld.com/56914/open_hole_with_wire.jpg">
So, I pulled a piece of stiff steel wire out of a wire brush and clamped it in vise grips. Then I pushed the wire into the hole while I heated with a soldering iron. When the wire finally pushed through, I kept moving the wire back and forth to keep it from being soldered in place while I removed the soldering iron. That kept the hole open.

I bent the leads on the new lamps so the bulb would remain centered between the holes. I inserted both bulbs and soldered the leads with as little solder as I could manage. Then snipped off the excess wire.

I cleaned the end contacts on the board with electrical contact cleaner and snapped the board back into the module being careful to align the bulbs with the holes in the white plastic bezel. I reinstalled the module cover and reinstalled the module in the instrument cluster.
<img src="http://pictureposter.audiworld.com/56914/smoke_test_before_reassembly.jpg">
I installed the instrument cluster back in the dash and turned on the ignition before buttoning up. Success. I've never seen the gear shift display in this car before.

SoCal Avanti

Correction to above advice: Fluid is checked while engine is running!

Bmthorn

First I removed the knee bolster and tested the terminals underneath to find one that came on with the ignition. If you use a compass mirror you will probably want it to come on with the ignition. If you just use an autodim mirror without a compass you could probably look for a terminal that comes on with the lights.

Then I took off the sunroof control panel and 'a pillar' trim. I ran A wire from the ignition terminal under the knee bolster up through the 'a pillar' then routed it above the head liner and made it come out in the opening for the sunroof panel.

Pin 1 (white) on the mirror is power, and pin 2 (black) is ground. This is the same for any auto dim rear view mirror.

I got the ground from a bolt in the sunroof panel and the power from the wire I ran up from the knee bolster.

The mounts are the same if you have a 94+

<img src="http://img232.imageshack.us/img232/6105/autodimbc9.jpg">

Updated for side mirrors:

This mod could cost as much as $600 unless you're getting some good deals*. For that reason I'm going to assume most people won't attempt this and it's not worth my time going to far into depth.

*I paid $50 for ALL the parts for the side mirror conversion, $75 for the rear view mirror, and did my own paintwork.

If you can figure out how to put these parts together to make a full mirror...
<img src="http://img377.imageshack.us/img377/4341/autodimparts2gt6.jpg">

Then here is what you'll have to do to wire them up.
<img src="http://img329.imageshack.us/img329/7904/mirrorwiringsd4.jpg">

If you're serious about doing this yourself I'll have no problem helping you out along the way.

Bmthorn

When I am working on or cleaning my car I like to listen to music. To have the music play you need to have the key in the accessory position. This causes the door buzzer to go off and it doesn't keep a good beat 99.983% of the time so I removed it. Now I forget to turn my lights off occasionally. Although I've never drained my battery, and it's been 9 months, I decided it was time to figure out a better solution. I had my cluster out today and decided to figure out how to make the buzzer come on only if the headlights were on.

This is probably only useful if you have an aftermarket deck since you can turn on the stock head unit without the key at all. As far as I know this will only work on the 100, A6s have a different buzzer that's built into the cluster.

While the key was in the accessory position I covered up one pin until the noise stopped. Just like shown in the picture below 85 is the pin that disables the buzzer in the accessory position. If you only cover up this pin when the key is in the on position it will still buzz.

<img src="http://img214.imageshack.us/img214/8333/doorbuzzermodgv9.jpg">

Next I found that pin 15 controlled the on position. I ripped both the pins out instead of putting tape over them to finalize the deal. Problem solved!!!

<img src="http://img207.imageshack.us/img207/1016/doorbuzzermod2lh7.jpg">

With both these pins gone the headlight warning still comes on whether the car is on, off, or in accessory mode.

austinado16

I see below that a poster actually JB Welded his broken rain tray arms. I opted to replace the rain tray instead because I was able to get a used one, and because I didn't want to do all this work only to have to go back in and fix it right the second time.

Here are the steps I used to take apart the glass moonroof on my '96 A6 Sedan:

1)Slide headliner panel back out of the way

2)Tilt sunroof/moonroof up fully

3)Grab at the rear of the black velvet accordian pieces, and pull them out of their channel in the bottom of the sunroof/moonroof. They have a lip that is simply tucked into the channel right up against the glass, so pull towards you starting at the rear of the accordian and it will start to untuck. Get it to completely untuck from the sunroof/moonroof

4)Now, grab the collapsed accordian piece and slide it backward (towards the rear of the car) until it gets to a wide spot in it's lower channel and then you'll feel it want to come off. Take it off.....take both of them off.

5)Use a torx T-25 bit and remove the 6 (3 per side) torx bit screws that hold the sunroof/moonroof to the sunroof lifting mechanism. I marked mine so I could get the roof height back without much effort.

6)Now lift the roof up and off, and put it in a safe place.

7)Slide the sliding headliner panel back partially closed and then grab the spring steel bars that push out on it's nylon runner blocks. This will suck the blocks inward and you can lift the front of the headliner panel up a bit, then turn the whole panel a bit which will release the rear nylon blocks, and then it will come right out.

8)Reach back into the roof and grab the nylon strap that connects to the water channel and drag the water channel forward.

9)Once you get the water channel forward and into the sunroof/moonroof opening, you'll see it has nylon block sliders as well. You can push the pin out of one of the nylon blocks, and that'll release the water channel....and out it comes.

10)The arms that operate the water channel are just press in pins, so some finesse with a screwdriver and they will pop out of both side's lifting mechanisms.

11)I think the arms are pot metal and so you're screwed. I could be wrong, maybe they're actually aluminum. If they are aluminum, then they could be TIG welded. Otherwise, in my opinion, there's probably no real good and permanent way of welding them, and they are so small in diameter I don't think a braced sort of repair is possible either.

austinado16

For steel sunroof: 4A0 877 633.......$110
For glass moonroof: 4A0 877 633A.....$256