Installing the trip computer module
Well, the hard part is out of the way, now all you have to do is remove your stock minicheck module from your cluster and install the trip computer/autocheck module from the donor cluster.
1.) Remove the minicheck module. This is pretty simple once you have the cluster out of the car. There are three screws (one to the left of the 4 bulbs, one on the opposite side, and one below the white harness connector. Once they're removed, simply pull the module out of the cluster.

2.) Install the trip computer/autocheck module into your cluster. This unit uses 4 screws, 3 in the same positions as the minicheck with one additional screw (by the coding plug/country selector switch).
www.audihelp.com/mods/images/bordcomp/DSC01960t.jpg 
note 1: in the above picture you can see the little fuel range calibration wire/circuit board installed behind the gas gauge, this is where it goes, although, it will need to be calibrated for your car, so, you don't have to pop it in just yet.
3.) Install the proper coding card. If you got your cluster from a 1990-1991 Coupe quattro, you should be fine. However, if you got your cluster from a 1988-1992 80/90 the coding card will not be correct for your car. Some have modified the 80/90 cards to work in their 1993-1995 90 quattro, I however purchased the proper card.
note 1: as mentioned below, these are all quattro part numbers, FWD use completely different part numbers!)
updated '07 note: the closest matched card for a FWD '93-'95 90 would be the same card as the coupe quattro or '93-'95 90 quattro.

<< back to part 2forward to part 4 >>