My car wouldn't start because of a battery that would not hold a charge. So I had a mechanic replace the battery. He told me that the alternator was not working properly either but the car was running.
Since I didn't want to drive much with a bad alternator, I took the car to Adolfo Auto Center, because they had done a good job with previous repairs, and left it there to be fixed. A little while later, they called to say that there was no problem with the alternator and I could pick up the car. When I got there they told me there would be no charge.
I am very impressed. In addition to doing a good job repairing my car previously, I really appreciate their honesty. They could have told me that they had replaced the alternator. I would not have known the difference.