Hooking up a remote starter to a '73 BMW 2002 is a cinch if you use the diagnostic plug located below the fuse box.
Pull the plug cover and find pin #7. If you look closely, you will find a small number beside each pin. As you lean over the left fender, pin #7 should be on the upper left corner of the plug. Clip a paper clip to one lead and, bending the clip, insert the other end into pin #7 carefully. The other lead clips to the positive battery terminal.
After making sure the transmission is in neutral and the handbrake set, flip the switch and the engine should crank.
Author: John P. McKay, Jr.