Some modern alternators only have one wire as all the external functions are housed within the alternator and, as the alternator is fixed to the car engine, this completes the ground circuit. However, the majority of alternators have three or four terminals which wires connect to.

What are the three wires on an alternator?

The three wire types in a three-wire alternator include the battery positive wire, the voltage sensing wire, and the ignition input wire. The battery positive wire connects to the starter. The voltage sensing wire connects to the battery, and the ignition wire connects from the alternator to the key switch.

What wire runs to the alternator?

The wire from the relay to the alternator is the main charging wire.