As mentioned earlier, alternators have a tough job. Every year, cars are built with more and more complex electrical systems and devices. The alternator is the car part responsible for supplying the power to the battery that keeps them all running. Starting the car and using the radio, the on-board navigation system, the heated seats, power mirrors and windows and any other electrical equipment will decrease the alternator's longevity.
Earlier, we described the action that generates electricity as a rotor spinning past coils inside the alternator. That rotor is spun on a needle bearing, an auto part which can break due to excessive wear or dirt and grime that can build up inside.
In addition, the diodes inside the voltage regulator can fail after time. Heat from the engine also puts an extra strain on the part, decreasing its car part longevity.
In other words, an alternator is an auto part that cannot last forever. Because there are so many factors that can affect its life, it's hard to say exactly how long an alternator can actually last. It depends on the car, the engine, the conditions in which it's used, how much electrical equipment it's regularly operating and so on. Some cars may lose an alternator at 40,000 miles (64,374 kilometers) while others may continue to operate well after 100,000 miles (160,934 kilometers).
When your alternator is on its way out, you may start to lose power to your various electrical components when your car is at idle. This is because there's nothing to recharge the battery. You may be able to get a quick jumpstart from a friend or helpful passerby with jumper cables, but the car won't last very long with a dying alternator. It's extremely dangerous to drive this way and you should try and make it to a repair shop immediately [source: Money Blue Book]. Service shops usually have all the auto part information they need about your particular alternator to determine what's going on.
In the next section, we'll discuss alternator maintenance, as well as ways you can avoid a breakdown by minding your alternator's health, along with that of the battery.