2003 Airconditioner belt replacement

My daughter had an 03 Trailblazer with the 5.3 liter V8 in it. The serpentine belt is a breeze to replace but the airconditioner belt is driving me up a wall. We move the tensioner over all the way yet the belt still won't come off. Am I missing something here?
Thanks
Mark

Does the adjuster loosen it up any?
If you are replacing it and all else fails cut off old belt.

I thought about cutting the old belt off but was afraid I would not be able to get the new one back on. I feel like we are moving the tensioner as far clockwise as we can. I can actually get the belt off of the whell on the tensioner but there is not enough slack to get it off of the air conditioner and it has to come off of it first to get off of the crankshaft pulley.