Even if you don’t have the jack the car up, it’s easier to work on an even surface. Ensure the vehicle is park, or has the parking brake engaged (if equipped with a standard transmission).
Working on the alternator without disconnecting the battery could result in getting shocked or damaging the vehicle. You can leave the positive cable attached.
Be sure the parking brake is on and the wheels are blocked before you jack it up. Insert jack stands beneath the vehicle for safety once it’s jacked up.
The bolts will likely require standard sized sockets or wrenches in American made vehicles, and metric in most foreign applications. The only other cable running to the alternator connects to a harness, so it will be easy to identify. Set the bolt aside someplace safe until you install the new alternator.
Be careful if you use a screwdriver to get to hard to reach clips so you don’t break the plastic. Tuck the loose wire aside so it doesn’t snag on the alternator when you remove it.
You can tell if your vehicle uses an auto-tensioner by looking at the alternator mounting bracket: if the bolts can slide from side to side in the bracket, it does not have an auto-tensioner. You will need to slide the belt off the alternator pulley before you release the auto-tensioner. Prior to making any changes, take photos of the belt set up so tha you know exactly how the belt should be routed around the various pulleys. In some cars, you might need a friend to relieve the tension while you remove the belt.
As you loosen the bolts, the alternator will slide in the bracket under the tension of the belt. Only loosen the bolts, but do not remove them! You may not need to remove the serpentine or accessory belt if it’s not damaged.
If you find any of those issues, you’ll need to replace it.
You may need to wiggle the alternator around some things in order to remove it. Keep track of how you worm the alternator out of the engine bay to help squeeze the new one in.
Even if you provided specific information when purchasing the alternator, this step is important to make sure they provided you with the correct part. If they don’t match, return the new alternator to the auto parts store to get the correct replacement.
Be careful not to trap any wiring behind the alternator as you slide it into place. Watch out for the serpentine belt as you slide the alternator into place to be sure you don’t damage it.
You’ll need to tighten the belt using the alternator later if you don’t have an auto-tensioner. Make sure the bolts are snug enough to hold the alternator in place, but loose enough to slide side to side in the bracket.
Keep the tensioner loose with pressure on the ratchet. When the belt is properly seated in the various pulleys, slowly release the ratchet, allowing the tensioner to once again place tension on the belt. If there is no diagram stuck in the engine bay, you may also be able to find the diagram in your vehicle owner’s manual. You might also be able to find the diagram on the manufacturer’s website.
Be careful not pinch or cut any wires with the screwdriver or pry bar. You or a friend will need to continue applying pressure until the bolts are tightened.
Make sure that the serpentine belt has less than an inch of play back and forth once installed. If the belt is a little loose, loosen the bolts and apply pressure again using the pry bar while you tighten them up. If you have taken photos of the belt, use them to make sure once again that the belt is positioned correctly.
Make sure the primary power cable is tightened firmly onto the new alternator. Be sure you hear an audible “click” from the wiring harness to ensure it’s seated snugly.
If the battery is dead, you may need to jump start it. If the vehicle is jacked up, remove the jack stands and lower it.
