An alternator is an auto part that transmits power from the fuel system to the battery for operating vehicle accessories, such as the radio, headlights and air conditioning fans. A wire called an exciter generates the voltage needed for an alternator to start working once a vehicle is started.
Generally, three wires are connected to an alternator, including the exciter wire. The exciter, which is a low-voltage generator that transmits DC power, sends electric current directly to the alternator.
If the exciter wire is disconnected or not working properly, it will not transmit voltage to the alternator, and as a result, the alternator will not generate enough power to operate accessories. Initially, alternator failure may not cause any symptoms since a vehicle’s battery has some reserve power, but eventually, the reserves are depleted and accessories like the radio and air conditioning will stop working.
The alternators on most modern vehicles have internal voltage regulators; therefore, they don’t need an exciter wire to function properly.