I took my Powermaster 75a (60a/99a) alternator into NAPA this afternoon to test it. Since that unit was not in their computer, we picked the highest rated unit that we found on the list (65a). The test was attempted three times and each time it told him to check the grounds. So I walked out with no answer.

Is there something the parts stores can do to test an aftermarket alternator if it is not listed on their computer?

Thanks