My car's alternator was not properly charging the battery. After explaining to the owner that my existing alternator had tested (off the car) and passed, I asked that he give his recommendation. After troubleshooting the car, the shop owner called and said the alternator did not work. I trusted his opinion and agreed to replace the alternator. The "faulty" alternator was under warranty so I took it to Advanced Auto Parts for a replacement. Advanced Auto asked to run a test on the "faulty" alternator. This test showed that the "faulty" alternator passed and was okay to be used. Per my request, Advanced Auto agreed to give me a replacement alternator even though the faulty alternator was indeed functional. I took the replacement alternator to the shop owner. The shop owner installed the replacement alternator and called that the car was working again. I paid World Japanese Auto in full $175 for his services. I then started my car testing his work. The car did crank but after the air conditioner was engaged, the car battery light came on. This proved the alternator was not charging. I went back into the shop to communicate my findings. The shop re-evaluated the car and told me the crank pulley was cracked causing slack in the serpentine belt. This slack was causing the functional alternator to not charge properly. The shop owners diagnosis of a faulty alternator was incorrect and he refused to return payment for his services.