They have the tools, but most of the counter people do not really know how to use them very well.
If you have an AC/DC volt meter (even the cheap/free harbor freight ones will do for this) you can do a quick test. Check battery voltage with the engine off, now test it with the engine running.
EOV - 12.6 VDC on a fully charged good battery.
ERV - 13.6 - 15.0 VDC with a good alternator.
Switch to AC and you should see less than 1/2 volt AC. any higher and the rectifier has at least one bad diode.
https://www.2carpros.com/articles/how-to-check-a-car-alternator
Thursday, August 3rd, 2017 AT 6:44 AM