Engine Compartment Wiring - vw-resource This provides the wiring to the indicator light, which is an essential sensing part of the alternator internal wiring. See the wiring diagram above ("Rough Schematic of Engine Wiring") for the alternator with an internal voltage regulator. Alternator and Engine Compartment Wiring Voltage Regulator - vw-resource The really early 6-volt models had the voltage regulator mounted on the generator. '71 and '72 alternators had an exterior regulator, and '73 up have the internal one. Much simpler wiring. The generator regulator has 2 or 3 wires on each side of it, some coming out of the hole at the rear where the harness is.