Well, if your MBZ is a '76 then it's below the dashboard on the left
hand side in front of the hood release. It's mounted on the same bracket
as the pedal that sets the emergency brake (I had to tie mine to the
bracket because it kept popping out of the socket after the emergency
brake pedal was released enough times - maybe that's your problem too).

There's a cardboard covering underneath the dashboard that you have to
remove first but that's simple enough to do.

ron