One of the most common failures is bearing failure. The needle bearings that allow the rotor to spin freely inside the stator can break down from dirt and heat. When the bearings fail, the rotor will not spin efficiently and can eventually seize. Usually an alternator with bearings failure makes a loud grinding noise.
Do alternators charge at idle?
Basically, at idle you can probably get 80 amps out of your alternator. You can charge a flat battery to 80 percent full in about 2 hours, so long as you alternator can manage produce around 14 volts at the battery terminals this whole time. Depending on what the battery is demanding.
How often do you replace an alternator?
The battery’s job is to start the car, and the alternator keeps it running.” Gunning says an alternator typically lasts about seven years, or about 100,000 to 150,000 miles, adds Waits. Some mechanics, though, say they typically see alternators last about 80,000 miles.