As soon as I walked in the broken alternator that my brother and I pulled off of his 2000 Nissan Altima, the first thing he did was take the alternator and hook it up to his machine to make sure that it was the alternator that failed. While he was operating the machine he educated on what the machine does and how it checks if the alternator was or was not working. Since the alternator was not working he went to get the same exact alternator from his back room to exchange it with our failed alternator. Even before I had walked out of his shop with the new alternator in hand, he explained to me that the battery has to be fully charged, he even pulled out an alternator that he was currently working on to show me what would happen if the battery is not fully charged. All in all he provided us with great service.