WARNING: This page is about a different car, the 1995 Mercedes-Benz S500, 1995 Mercedes-Benz S420, and 1995 Mercedes-Benz E420. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Charging System Wiring Diagram (E420)
Fig 2: Charging System Wiring Diagram (S420 & S500)