How to Wire an Alternator

Alternator wiring appears difficult on the first inspection. There are several wires running in and out of the alternator that must be hooked- up to allow the unit to function. The only wires that should be disconnected during replacement are the positive lead to the battery (for charging the battery while engine is running). And the positive and negative wires providing a ground source and power to vehicle accesories.The only wires that should be disconnected are the input line from the alternator to the battery, grounding strap (usually internal needing no repair) and the positive lead that powers all functions in the drivers compartment. Here's how you do it.

Difficulty: Moderate

Instructions

Things You'll Need:

• Open end box end wrench.
• Safety glasses.
• Face shield (as needed).
• Splicing and connecting tool (as needed to replace faulty wiring).
• Wire connectors (as needed to repair wires).
• Digital volt ohm meter (to check battery voltage and alternator output).

Hooking up alternator wires

1. Do a visual inspection in and around the alternator. Check for burned or heat damages wiring. Look for bare wires and disconnected wire. Use your mechanics mirror to look behind the alternator and check for defects. Repair any damaged wiring with your wire splincing/connector tool before attaching the alternator wiring. Make sure the leads themselves are free of corrosion or damage. Replace as necessary. Disconnect the negative battery terminal to prevent electrocution and damage to sensive components.

2. Once all external wires have been inspected and repaired, use you open end box end wrench to loosen the large nut on the alternator and remove. Place the eyelet over the bolt and secure the mounting nut using your open end box end wrench. This lead is the larger of the two leads connected to the alternator. They are typically red and white although colors differ according to your year model vehicle.

3. The second terminal provides power to the instrument panel and accessory functions. The color of this lead is typically red. This wire sends power to all accessories in the vehicle. Remove the nut from the power terminal. Install the red lead over the bolt threads and secure with the nut removed previously.

4. Connect the negative battery terminal that you removed earlier. Check for corrosion on the battery terminals and leads. Remove any corrosion with battery cleaner and a wire brush.

5. Test operation of the newly installed alternator by starting the engine. Listen for growling noises, dim dash lights and low battery charge. Check the wire terminals for corrosion and debris. Remove all debris and try starting the engine again. If the alternator is still not functioning properly, return the alternator to the parts house you bought it from and get a new or rebuilt unit.

Tips & Warnings

• Wear safety glasses and face shield (as needed) throughout this procedure.
• Disconnect the battery ground before beginning the procedure.
• Keep hands away from a running engine.
• Remove any loose close or jewelry to prevent an accident.
• Safety glasses should be worn throughout this procedure.
• A face shield should be used when examining the battery and removing wire leads.
• Do not stick your hands or anything metal over the battery or alternator. You become the ground and can receive a sever shock.
• Do not wear rings or any jewelry during this procedure. Tape over your wedding ring so it will to cause a grounded circuit and weld your-ring to your finger.

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