* Large Gauge Wire (usually red or orange): This is the Battery Positive (+) wire. It's the thickest wire and carries the main charging current from the alternator to the battery. This is usually the easiest to identify.
* Medium Gauge Wire (usually light green or yellow): This is the Exciter wire (or "sense" wire). It's a smaller gauge wire than the battery positive wire, and carries a low current signal that tells the alternator how much power to generate. This wire usually goes to the voltage regulator, often integrated into the alternator itself. You may see this as a smaller connector or separate wiring to the control system.
* Small Gauge Wire (usually black): This is the Battery Negative (-) wire (ground), but the ground may also be the case itself. This one is smaller, providing the ground path for the alternator's circuits. It's important to note that some alternators have a separate ground wire from the case for the control circuit, in which case the case might not be a ground for the exciter circuit. If the alternator doesn't have a separate ground, the alternator's case needs to be properly grounded to the engine block.
How to Verify:
1. Consult a wiring diagram: A wiring diagram specific to your 1995 Jeep YJ is the most reliable method. You can often find these online through Jeep forums, repair manuals (like a Haynes or Chilton manual), or online auto parts store websites.
2. Use a multimeter: With the ignition OFF, you can use a multimeter to trace the wires. The large gauge wire should show battery voltage when tested to the battery positive terminal. The small gauge wire should show a good ground connection to the engine block or chassis. Checking the exciter wire requires a running engine, and you'll need to understand that circuit's behavior to correctly interpret the multimeter reading.
Important Safety Notes:
* Disconnect the battery negative terminal before working on any electrical components. This prevents accidental shorts and damage.
* Always double-check your work before reconnecting the battery.
* If unsure, consult a qualified mechanic. Incorrect wiring can damage your electrical system or even cause a fire.
Don't rely solely on color-coding. Use a combination of wire gauge, location, and ideally, a wiring diagram to positively identify the wires.
