Most new or refurbished alternators, including those made by Bosch, have built-in voltage regulators, while older types of alternators use an external regulator. Alternators produce variable amounts of voltage based upon the speed the rotor turns, but your car's electrical system operates on a set voltage, usually 12 volts. Once the voltage output from the alternator reaches about 13 or 14 volts, the regulator cuts in and maintains the voltage. External Bosch regulators generally have two plug-in terminal sockets -- one wired to the alternator and the other to your car's electrical system -- so you will find it a simple task to wire up your Bosch voltage regulator.
Disconnect the battery cables from your battery before wiring your Bosch voltage regulator. Loosen the nut and bolt on the end of the black battery clamp using a wrench, then lift off the cable clamp from the battery terminal. Do the same for the clamp on the end of the red cable.
Locate your Bosch voltage regulator; it's cylindrical and sits on top, or to the side, of the alternator. Find the two plastic sockets on the back of the regulator; they are different sizes, making wiring easier.
Find the two sets of wires near the Bosch regulator. Both have plastic plugs on the end and both have several coloured wires attached. One set of wires connects to the alternator and the other set goes into a larger wire harness and connects to the electrical equipment in your car.
Insert the plastic plug on the end of the wires that go to the alternator into a plastic socket on the regulator. The plug only fits into one socket, so you can't get it wrong. Push the plug into the socket using your fingers until it snaps into place.
Insert the remaining plug on the end of the wires that go to the electrical system into the remaining socket on the regulator.
Reconnect the clamp on the end of the red battery cable to the positive terminal of the battery using a wrench; it's clearly labelled. Reconnect the clamp on the end of the black battery cable to the negative terminal.