Yesterday, my wife's car (a 2009 Toyota Sienna AWD) wouldn't start, and this came clear out of the blue. A jump fixed it. We let the car sit idle for a good 30 minutes, and it was able to start up later in the day. Today, it needed another two jumps, and I took it to AutoZone to get the battery tested. It was an old battery and it came up bad, so I bought a new one.
We ran the tester again, and it said that the alternator was good but that the voltage regulator was bad. He said it was odd, because it was still showing 13.48V at load. I took it home and ran some tests:
- Battery voltage with car off: 12.7V
- Car idling: 13.49V, and voltage increased steadily over time
- Car idling with all accessories on: 13.2-13.3V
- Car revving at 2000 RPMs with all accessories on: 13.4V
Any idea if this would indicate a bad voltage regulator? The steps I saw online made it sound like this would check out, but I'd welcome feedback.