My battery died the other night,I pulled thealternato andtook totwodifferent auto parts stores.The first said it was bad the other said it was good. I replaced the battery and put the alternator back in. Now when I turn the ac on the ac pulley skips andit squeeks continuosly. It seems thetensioner is as tight as it can be and I've had no problems with the AC. It is a 2004 and only 40000 miles. Any sugestions?

 

Are you sure they are aligned properly? If you put a straight edge across the front edge of all the pulleys, they should be aligned. If you put the alternator back in place a little too far front or back, or crooked, it could be causing the belt to be putting sideways (actually front to back) pressure on the belt and that could make it slip.