Serpentine belt tensioner 98 sebring conv.
 

Could someone please tell me where the nut is to release the serpentine belt ? I can't find it. I tried the nut on the idler pulley but that does not move. 98 sebring convertable 2.5 Thanks

On almost any belt-driven system, there will be a method for tightening the belt that involves moving one of the pulleys through an arc. The pulley that moves will have a pivot point and a locking method. What you usually find is a curved slot along the arc that the locking bolt slides in. At the center point of the circle defined by the arc is the pivot point.
Generally speaking, you will need to loosen a bolt at both of those points. If you are loosening only one bolt, the pivot action won't happen.
This advice applies to automotive belts, washing machines, furnace blowers and a whole lot more.