The individual auto parts within the alternator like the rotor, diode pack and stator typically aren't serviceable. This means that when one of the car parts go bad, it's best to replace the entire alternator. If you have the tools and some knowledge of how to repair a vehicle, you can save some of the labor costs by changing out the alternator yourself. Just remember that it's always a good idea to consult your vehicle's service manual for the right auto part information.
To begin, make sure the vehicle is parked in a flat, well-lit area and that the engine has had proper time to cool down. Next, disconnect the battery to minimize the risk of shocking yourself. Locate the alternator in your engine bay, usually a silver, rounded device with a fan visible behind the belt pulley. It's bolted to a bracket attached to the engine, so you may need to use two socket wrenches to get it loose. If the hardware is corroded, it may be difficult to remove the bolts.
Alternators can be driven by two types of belts connected to the crankshaft -- a V-belt or a serpentine belt. The former fell out of fashion after the late 1980s and most new cars use a serpentine belt. You'll need to loosen the belt tensioner so there's some slack in the belt, then slip the belt off the pulley. It's not a bad idea to replace the belt altogether while you're at it. Just remember to contact the local auto parts store with you car part information to make sure they have the right part in stock for you.
Now, remove the electrical connections behind the alternator, making sure you remember where they were located. You can then remove the old alternator and set it aside. Now, if you're replacing the belt, do that before you do anything else. Place the new alternator in the correct position and secure the belt, making it properly tight -- then you can begin to tighten the bolts that hold the alternator in place. If you're working alone, it may help to use vice grips to hold the alternator right where you want it [source: Mobil Oil USA].
Now, replace the electrical connections, being careful to put them in the proper place. Reconnect the battery and start the engine. Make sure you don't get any engine or battery warning lights on your dashboard and that you don't hear any unusual noises, either. If you do it right, you'll be rewarded with car part longevity -- your new alternator should perform just as intended.
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