An issue with an alternator usually results in the battery charge light coming on while driving. If your vehicle is having trouble turning over and the battery is in good condition, this could indicate a problem with the starter motor.
If your alternator is having trouble providing energy to your car, it will most likely be replaced rather than repaired.
When an alternator is replaced, the technician will first inspect and test the alternator output, charging system, and drive belts. They will disconnect the battery, then remove and replace the alternator. Finally, they will reconnect the battery and test the output again to ensure everything is now running smoothly.