Alternators seldom experience a total failure, but the relatively low cost of completely re-conditioned units has virtually eliminated any need for the do-it-yourselfer to try to repair an alternator – they are simply replaced.
Starting in the early 1960s, alternators began to replace generators as the standard means of charging your vehicle's battery. Like generators, alternators are belt driven from the crankshaft pulley of the engine. Today, two basic types of drive belts are used: The V-belt and the serpentine (ribbed) belt. The V-belt belt design predominated until the late 1980s, but today most vehicles use a ribbed, serpentine belt. Since serpentine-belt-driven alternators vary substantially in how the belt is held in "tension," replacement techniques vary quite a bit. This DIY article will concentrate only on the older, V-belt-driven systems.
When replacing the alternator, you will need to decide between purchasing a new alternator from your vehicle's dealership or buying a rebuilt unit from an auto parts store. The cost difference is substantial, so weigh the pluses and minuses before you buy.
Park your vehicle inside or outside in a well-lighted, well-ventilated, level area. Locate the alternator under the hood in the engine compartment. Here are some hints:
- The alternator is always belt-driven off the front of the engine, even on transverse-engine, front-wheel-drive vehicles.
- The alternator has electrical wires running to it.
- Most alternators are made of aluminum.
- Most alternators have a small, built-in fan visible behind the belt pulley.
Once you have located your vehicle's alternator, carefully note how it is attached to the engine. There should be two points where the alternator is bolted to the engine (one that allows the alternator to swivel or swing to vary the tension on the V-belt, the other, usually a curved bracket with a long slotted hole in it, that limits the amount of swivel and locks the alternator in place).
Make sure you can reach these bolts with either socket or combination wrenches. In many cases you must use two wrenches – one on each side of the bolt – to loosen it. If the bolts/nuts appear to be corroded, test your ability to free them.
If you cannot locate the alternator, reach the attachment bolts or free the nuts, stop and let a professional technician handle the job.