Alternator Replacement Instructions


Alternators rarely fail, but when they do, they require replacement. It's the battery's job to start the car and provide power on demand. The alternator is what keeps the battery in shape. Batteries will fail more often than an alternator, but if a bad battery can be jumped to start the car, the alternator will provide enough energy to keep the engine running. This isn't true on the other side of the spectrum. Batteries only have reserve power in them, so when the alternator isn't providing recharge to them, the battery will die and so will the car.

The Drive Belt and Alternator Access

  • The first and obvious task to replace an alternator is to locate it. While visible and easily accessible on many vehicles, other engines can pose a challenge. In some applications, the alternator is located at the bottom of the engine, which will require lifting the vehicle and, in most cases, removing a wheel and possibly a splash shield to access.

    Once the alternator is located, you'll need to remove the negative battery terminal from the battery to disconnect electrical power to the alternator, much like you turn off an electrical breaker before repairing an electrical outlet.

    Most vehicles nowadays employ a serpentine belt that snakes around the multiple onset pulley system. Some imports and many older vehicles use offset pulleys and two or three belts attached to the crank to power all the different electrical and powered options using V-belts. In any scenario, the belt wrapped around the alternator pulley needs to be disengaged. Serpentine belts employ an automatic belt tensioner that is pivoted using a tool to relieve the tension on the belt and allow removal. You do not need to remove the entire belt--just remove it from the alternator pulley. V-belt applications can offer a couple of different options to remove the belt. Commonly, two alternator adjusting bolts are loosened along a sliding bracket and allow you to reposition the alternator to relieve the belt tension. On some older imports, you may need to loosen an adjusting screw and then loosen the idler pulley bolt to get it loose enough to wiggle and manipulate the belt off of the pulley.

    Once the belt is removed, it's time to disengage the electrical connections. Typically, these connections are quite visible. Some may require moving a red-colored cap to access the retaining nut of the wires. There will also be a plug connection to the alternator and this is commonly located on the back side of the alternator housing.

    Most alternators are held to the engine block by two to the three bolts. Any brackets in the way blocking access to these bolts will need to be removed. Once the bolts are removed, the alternator can then be removed. There are some alternators that employ tight bolt bushings and require being pried out of position to remove.

    To replace the alternator, reverse the order of the procedure in which you removed it.

    For V-belt applications or some imports that may use smaller ribbed belts, be sure to set the proper tension of the belt before completing the procedure.

Recharge to the Battery

  • An alternator provides recharge to the battery for the amount of energy the battery expelled to start the car and the remaining energy demand being used--such as lights, A/C, radio and any other electrical options. An alternator is not an automatic battery recharger. If your battery was sucked dry by the bad alternator, internal damage to the battery may have occurred. To protect further damage to the battery or to the new alternator replacement, it's a good idea to recharge the battery fully with a battery charger.


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