It's early in the morning. You have an appointment with the company president. This is the deal you've been waiting on. You're looking sharp in your new business attire. You're about to leave, go to your vehicle, put the key in the ignition, and OMG!!!!!
Your vehicle won't start. What the heck??? This is the last thing you need on a day like today. You start to ask yourself questions. Self, why didn't my car start? Did I leave something on? At this point, it doesn't matter. Your vehicle needs an alternator. After the dust has settled, you're handed a bill for four hundred dollars. OMG again!!! What did the mechanic replace for four hundred dollars, and how can I prevent this from happening again? There isn't an easy way to get around not repairing your vehicle. But, paying attention to the symptoms of your vehicle will help cut down repair cost.
The charging system isn't a complex operation. There are many invisible variables that can affect its operation. The most popular method for testing an alternator is at the battery. But, this test can't reveal the common problems that exist inside of an alternator. The common problems are open or shorted alternator diodes, intermittent high or low charging rates, charging system wiring problems, intermittent cranking/no start complaints or intermittent dead battery complaints.
The alternator operates off a magnetic field. This magnetic field is created by a rotating magnet called a rotor. The magnetic field is "cut" by three windings of copper wire. An alternator has a positive and negative diode which rectifies the alternator's electrical output from alternating to direct current. As the magnetic field is created, the current passes through a carbon brush. This activity is controlled by the voltage regulator. To accomplish this operation, the voltage regulator must be able to accurately sense battery voltage. By checking your battery cables (positive and negative), this will help your alternator's ablility to charge your battery. The state of your battery is very important to providing voltage to the voltage regulator. Bad battery, your alternator works harder. Lose cable connections, your alternator works harder. In turn, this will wear out the wiring, and brushes inside of the alternator.
Alternators are capable of creating an intermittent high charge or low-state-of-charge problems. An intermittently high charging rate may store a trouble code in the vehicle's computer or a repeated failure of the high-beam headlamp bulb. Low state-of-charge issues are indicated by intermiitent cranking, no-start complaints in sub-freezing temperatures, intermittent dimming of headlamps or battery sulfation.
Alternators will wear out over time. But, listening and understanding how a system works will help you and your pocket in the long run.