My XB was squealing a little bit, I am not used to working on new cars, but like I usually do, I loosened the alternator lower bolt and upper bolt and use a pry bar to pull the alternator forward a little bit. The squealing has stopped but now I have learned that the newer cars uses a serpentine belt and auto tensioner? So was I supposed to make the adjustment in the auto tensioner instead of doing what I did?

But then if the tensioner was "auto" then it wouldn't squeal or have much adjustment, would it..?

 

not all cars use an auto tensioner what you did is correct.