There is either a square hole in the tensioner for a breaker bar or a hex protruding from it that you can place a wrench on. Just pry against the spring tension.
if you remove the moter Mount it is more accessible.
Assuming you have a serpentine belt on that 3.3L engine, the tension on the alternator would be controlled by the idler (tension) pulley. The alternator is stationary.
There is no fixing it. It must be replaced.
Remove the alternator wiring harness. Loosen the tensioner pulley. Remove the alternator belt. Remove the alternator retaining bolts. Reverse the process to install the new alternator.
Loosen the tensioner pulley. Put the belt around the alternator pulley and the tensioner pulley. Move the tensioner pulley to the right until the belt is tight. Tighten the tensioner pulley.
Buy a Chevy!!!! That was a big help. Most but not all serpentine belt systems have a spring loaded tension pulley that just holds constant tension on the belt. If there is a tension pulley, it will be the one pulley that is not attached to anything like the alternator or AC. After that, the alternator is the most likely to be the one that adjusts.
Most cars now have a serpentine belt that drive the alternator, water pump, power steering unit, etc. The belt tension pulley is a spring loaded pulley that keeps the proper tension on all these units. It can be moved to release the tension in order to remove the belt.
Look at the top and left of the motor. It's easy to get to. The tension pulley is right below the alternator.
Yes, it is used to adjust the tension on the A/C compressor. Looking into the engine compartment from the passenger side it is to the left of the alternator. To adjust tension you need to loosen the bolt which holds the pulley and then adjust the bolt which is directly above the pulley. Once you have proper tension tighten the pulley bolt.
Release the tension using a wrench etc from the idler pulley.
All you do is look for the tension pulley and tighten it, see below
loosen the tension on the belt with the tension pulley, remove the belt then disconnect your wires from the alternator then take the 3-4 bolts, holding the alternator on, off. then do the opposite to put the new one back on