I'm on a mission to see if a 2002 Mercedes C COMAND Navigation Head Unit will work on a 2003 C 240 system? I tried the unit today and sort of failed, 2 out of the 3 harnesses worked. The Navigation and radio worked... but not the cd or changer.? It's got to do with the 3rd harness ( different pin connectors ). has anyone come across this problem? is there some sort of adapter?