There's probably no such thing as a fun car repair. Any time your car fails, it can be frustrating, disappointing, and disruptive. Unfortunately, faulty alternators are one problem that many car owners will experience sooner or later. With new cars lasting much longer than their older counterparts, the 100,000-mile lifespan of a typical alternator no longer seems quite so far away.
Alternator failures can be particularly challenging to deal with since you may initially suspect electrical gremlins or even battery problems. Learning the common causes and symptoms of alternator failure can help you to recognize and repair this problem before you find yourself stranded on the side of the road.
Why Good Alternators Go Bad
Like any part of your car, your alternator will eventually wear out. The rapid and repeated heating and cooling cycles of your alternator make it particularly susceptible to wear, however. Inside your alternator, a magnetic component called a rotor spins quickly inside of the stator to produce electricity. The rotor relies on a set of bearings to spin smoothly and a set of diodes to convert its AC output to DC.
While there are a variety of potential failure points for your alternator, the two most common are the rotor bearings and the rectifier diodes. If the bearings fail, the rotor can no longer rotate smoothly, compromising the ability of the alternator to continuously output power. Rectifier failure can also drain your battery or produce a variety of unusual electrical symptoms.
The alternator's pulley is a third, somewhat less common failure point. The pulley allows your vehicle's accessory belt to drive the alternator, converting your engine's mechanical power into electricity. Depending on the model of your vehicle, you may be able to replace the pulley without replacing the entire alternator unit.
Recognizing Alternator Trouble
Failing alternators can produce many symptoms, depending on the underlying cause. Bad rotor bearings can cause a grinding or squealing noises. As the problem worsens, you may experience dimming lights or failing electrical accessories as the alternator struggles to keep your battery fully charged. Testing the battery and the alternator can help to reveal the culprit.
Unfortunately, the symptoms of a faulty rectifier can be less clear-cut. When one or more rectifier diodes go bad, it can lead to a drained battery as well as unexpected electrical issues. If you are noticing a variety of seemingly unrelated electrical gremlins, then your alternator may not be fully converting its AC output to DC.
Repairing a Bad Alternator
Depending on the root cause of the problem, repairing your alternator may involve a complete replacement. Some older alternators can be disassembled and rebuilt to replace faulty parts. Whatever the core problem, driving with a bad alternator is never a good idea. Be sure to diagnose and repair yours before disaster strikes.