The following charging without trailer towing diagram shows the four-wire alternator wiring diagram illustration in 2D-space. As the following wiring diagram illustrates, a 4-wire alternator allows you to convert mechanical energy into electrical energy, especially in motor vehicles. In the below wiring diagram, we have a battery connected to the 120A alternator that passes the current to the IC regulator. The 3-wires from the IC Regulator are connected to the Engine Control Module, and the fourth one, the green one, is connected to a 10A gauge. Such complex wiring diagrams show the importance of having a 4-wire alternator in your setup.