How to Replace a Car's Alternator

by Contributor

Alternators are a car part that can be very costly to fix because of labor costs. But with an hour or two of time and a little elbow grease, any do it yourself car mechanic can install their own and save a few dollars.

Removing the Old Alternator

Pull your car into the garage or your work area. Turn the car off and let it sit for a while to cool.

Begin by disconnecting the negative cable of the battery.

Remove the serpentine belt from the pulley on the alternator. Do this by using a socket wrench to turn the serpentine automatic belt tensioner so that it allows slack in the belt. Then simply slip the belt off the alternator pulley.

Locate and disconnect all the mounting bolts on the alternator, use a vehicle specific manual if you have any trouble.

Disconnect all wires attached to the alternator then remove the alternator from the car.

Installing the New Alternator

Slide the new alternator into place. Do not worry about the serpentine belt yet.

Replace the bolts that held the previous alternator to secure the new one in place.

Attach the wires to the new alternator the same way they were attached to the old one.

Adjust the serpentine belt tensioner the same direction you did in Section One to put slack in the belt. Wrap the belt around the pulley of the new alternator and then remove the socket wrench from the automatic belt tensioner.

Inspect the belt to be sure it is not snug and follows the path required in the pulley and belt configuration diagram.

Hook the negative battery wire back to the negative terminal on the battery.


  • check Find the serpentine automatic belt tensioner by referring to the car's pulley and belt configuration diagram.
  • check Use a rubber mallet on the old alternator to break it loose if it won't move once you have removed the bolts securing it in place.
  • check Use a voltmeter to test the output of the new alternator and be sure it is functioning before driving the vehicle


  • close Be careful when removing the serpentine belt. As soon as it comes off the alternator, it will snap to its full tension position. If you are in its way, you may end up with a busted knuckle.
  • close If the serpentine belt is not put back properly, it will not be tight enough and the vehicle will not function properly.
  • close If you do not disconnect the negative battery cable, you may be shocked or damage the new alternator and other vehicle electronics.

Items you will need

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