00' saturn wagon 3.0 liter a/c and belt problem.

[crazydriverz]

Just bought this wagon and found out the belt comes out of alignment and starts to strip layer off when a/c is on. But when the a/c is off the belt will not move and run great with no problem. All pulleys seam in good shape. however the a/c compressor pulley seems to be small for a 5layer belt.im wondering if the compressor moves in and out...or something.it wont do it while sitting. Just when im driving. Any help is welcomed