yes sounds like it. but first check basic components in the charging system -- i.e. battery clamps, and especially grounds and don't forget the belt adjustment.

and remember an isuzu alternator can pass the tests at such places as autozone and still not be in working order.

standard boilerplate language concerning isuzu replacement alternators: "heed the advice in this and other forums. do not replace your isuzu alternator with a rebuilt unit from the bigboxpartsstores. they apparently do not test for nor correct special circuits within the alternator. even if the unit initially works, it will probably crap out and your lifetime warranty means a lifetime of replacing it over your lifetime. instead replace with a quality unit, i.e. new from dealer, rebuilt from dealer, rebuilt by bosch,(my favorinte for price/quality ratio) and i've seen posts by those who are happy with the rebuilds from NAPA."

//bc