I'm having a issue with battery charging. I took the battery and alternator in to get checked and both passed as good. Some times it will charge . My belt does squeeke. Was woundering if it could be b

The squeak could be coming from a bearing on any of the pulleys or the belt tensioner or idler pulley, as you have noted a problem with the alternator, double check that one by remove the serpentine belt and spin each pulley. Also check that the belt tensioner is doing it's job and keeping the belt in tension, if it slacks while driving that might be a reason the alternator is failing to maintain an adequate charge to the battery.

How do i check the belts tension?

with your hand make sure is not to loose or tight.if that is ok check your output on your alternator plug.

Thank you. What's to lose? And how do i check output? A nuther thing I noticed was on my fan pulley the slides a mm or 3