I'd like to continue the trip computer discussion started <a href="https://forums.audiworld.com/a6100/msgs/91060.phtml">here.</a> I've STFA but find only upgrades for 93-94 100s using parts from a TC equipped 92. It appears that the 95-98 C4 A6 never got the TC in North America. However, it's likely that A6s can be so equipped because 'corne' says all A6s through 98 had them in South Africa. Of couse, those are right hand drive and kilometers, I think.

I have instrument clusters for both a 96 A6 and a 90 200 with TC on my bench. It's interesting that the 92-94 100 upgrade parts that 'bmthorn' shows in his <a href="https://forums.audiworld.com/a6100/msgs/51513.phtml">picture</a> are visually identical to my 200. I'm guessing that Audi reused the same old IC circuit boards until it got rid of the mechanical odometers, i.e. through 94.

As I've done since I was a kid, I decided to take things apart to see how they work.

First of all, the 200 IC has a separate daughter board on which is mounted the Autocheck display and the TC display. The board also has 3 large integrated circuits. Two of them are NEC D7228AG and the board traces from them generally travel to the Autocheck display. Kinda makes sense because the Autocheck is a full graphical display and would need a lot of traces to drive the it. BTW, the Autocheck display itself is nothing but a glass LCD panel with polymer strap connections to the circuit board.

On the third integrated circuit I can't read the manufacturer or number but the traces run from it to the TC display. So that has to be the processor driving the TC. Again, the TC display is just LCD glass and polymer connections.

It's unlikely that VDO, the IC manufacturer, would build a completely unique Autocheck assembly for every configuration that Audi offers. That would be an inventory nightmare. On the circuit board is a small 5 resistor circuit soldered in. There are some traces running from all of the larger integrated circuits to it. Since it's marked 'VDO', I think this little circuit is used to specify things like gallons vs. liters and miles vs. kilometers. That would make it easy to reconfigure the circuit board for a different configuration. It also means that all of the calculation logic for all possible configurations would have to be contained in the existing integrated circuits.

Also interesting is the connector from the TC board to the outside world. There's just one 15 pin connector that fits through the back of the IC. It doesn't connect to the rest of the IC in any way. That's puzzling because I don't know how the wiper stalk switches feed to the TC board. Needs more investigation.

Now for the A6 IC. The Autocheck display is mounted directly on the main IC circuit board. No separate daughter board. It's a bit wider than the 200 display. Again, it's just the LCD glass and polymer connectors directly to pads on the main IC board. So, Audi must have built all the Autocheck logic into the main board for the A6.

Also on the main board, just below the Autocheck display, are a set of pads obviously intended for the TC display. There's also the unused instrument lamp hole there. It looks like the TC display just connects directly to the main board like the the Autocheck does.

So, where is the Autocheck &amp; TC logic. The main IC board has 2 large integrated circuits on it. The traces from the Autocheck display generally run to one of them and the TC traces run to the other. Both of the integrated circuits are labeled Fujitsu MB88636 plus other different numbers. That Fujitsu part is a 4-bit microcontroller, 3KB RAM, 16KB ROM with LCD driver built in. I'd guess that the other numbering means the code burned into ROM is for different purposes.

Some of the traces from the TC circuit seem to run to the large red connector on the IC main board. That's likely where the wiper stalk switch signals get to the TC.

Finally, here's my theory. Audi recognized that it was less expensive to design an IC board that would work in all markets and accomodate the TC as an option. I believe that the IC in the A6 can be upgraded with a TC by simply installing the wiper stalk with TC switches and the correct TC display. It doesn't matter what the TC display has written the front. The display values are determined by the logic on the IC main board and will display properly.

So, it's likely that an A6 TC display from any location can be transplanted into a US IC and work correctly. One from the UK, however, would be appropriately marked with gallons.

BTW: 96-97 A4s have the same wiper switch part number as the A6. Most of the V6 equipped A4s had TCs. It should be possible to use the A4 wiper stalk with TC switches in an A6. Maybe the harness would work too.

Sorry for the long winded explanation but I want to get some input from this forum. I know that some have upgraded earlier Audi 100s but I don't think anyone has done an A6.

You're comments?

 

A4 trip computer stalk should work.

 

YGM...and so, the great experiment begins.

 

Either way, good luck, sounds like a cool project.

 

... that the logic that actually does the calculations is in the instrument cluster main circuit board. The only part I really need from the UK cluster is the trip computer display. I will install that in my US cluster.

 

From what I know...when installing a B3 TC into a B4 the only required signals are the ones from the switch (up/down/reset) and a consumption signal (from the ECU) relating to MPG calculations. The rest of the information needed is already present in the cluster and fed to the TC through where the TC module plugs in.

I've only seen a 100/200 cluster pulled apart, but have never taken an A6/S6 cluster apart. But, if this is true what you are assuming about the A6 cluster having everything already installed except the screen (and switch) that's good news! I look forward to seeing your progress.

 

(Has a boost gauge instead of instant MPGs)...

 

<center><img src="http://www.showyourmedia.com/files/1215277830.JPG"></center><p>

 

Yes ours are right hand drive and kilometers and from the 100 (can out here in 1991) through to 1998 (when the last C4 A6 was sold) all of the 2.8 and 2.8E had them, not sure about the 2.6 es though, but according to things I read (can't remembet where) there are 3 little switches that can alter the display to either miles or kilometeres?? am I right or wrong, but I read it somewhere

 

I'm *assuming* a wiring harness from an B5 wiper stalk would be the same as for the C4 (plug-wise on the instrument cluster side) - from what I recall, all of the older cars use the same plugs).