New Belts are Streching?

[rover12]

I have installed new belts on my 89 classic, however the power steering and AC belts keep streching to the point that they slip. The belts have streched to the point now that theres now no room for tightening them. What is causing this?

 

[TyziskBen]

Belt tensioner pulley

 

[rover12]

I am attempting to reinstall the power steering/crankshaft belt and can't loosen the pivot on the power steering pulley. I have loosened the two bolts on the steering pulley pivot that the manual suggests removing. Is there another bolt that needs to be loosened? I can't get this pivot to budge.