Why is the belt shredding. on 1999 Ford Taurus

We changed the power steering pully,and the water pump. The Idler pully looks like it's at a angle to the engine and the belt walks then shreades. We have a wreaked 2004 Taurus for parts. Should I change the A/C clutch pully or the Idler???

Asked by for the 1999 Ford Taurus
idler must be straight to keep belt in line. start there

Thank you we changed the idler pully and so far so good. keeping our fingers crossed!