I have a number of new Mercedes ML Series Trip Computers A163 540 52 11 I have sold on eBay with instructions on how to install it yourselfin any ML that didn't come from the factory with one . Although they can also replace any defective unit that did come with one. To view a tour of the functions of the overhead onboard computer go to this link http://www.mbusi.com/gtour/gtour.htm If you would like a 620 kb email with adobe instructions on how to install the unit please feel free to email me at firstname.lastname@example.org There is a remote compass module that will give the trip computer a compass function. I have found the part number for the remote compass module 163 545 5732 and purchased one to photograph. If you have any info on the factory mounting location of the remote compass module, I'm offering 50.00 or a free trip computer , to the first person to email me photos of the factory mounting location and the wiring it plugs into. Thanks!