going craxy

My kids VW does the same thing. There's a tiny chip in the speedometer that controls the both of those. Well, on the VW anyway. You can either replace the instrument cluster, or have Audi replace the little chip. Either way, you will have to tear the dash apart.

Here's what I found from another post: You have to take apart the complete cluster n take the speedo and fuel gauge off. Then pull the needle for the speedo off. Under that is a little tiny case with the needle for the speedo. Under this case there are 3 sprockets very small about 1 cm big each. On the pin for the speedo there is a little coil with an end on it that lays in a certain spot. The end comes off and causes the speedo to go crazy.Put this back in place and you're set to go.

Here's a video that shows you how to remove your cluster. If you don't want to tear into it yourself, there is his website at the end of the video. You can send it to him and he will fix. Or buy a replacement from Ebay and just plug in the three plugs and away you go. http://www.youtube.com/watch?v=qcGJsGB40AQ

Did you check the dashboard and gauge harness ground wires connections. Make sure they are tight by adding a star washer between the sheet metal and the wiring end tab, so that the star washer digs into both the sheet metal and the wiring end tab. Also check to make sure the wires are tight into the ground connection tab.