I recently replaced my water pump and serp belt. After replacing, when I start my a/c after starting the car I get a really bad screeching noise. I turn it off and after about 5 minutes turn back on and no noise. I was thinking the belt isn't tight enough, but really have no idea

 

Check the belt, pretty common for people to try and eyeball it, leaving it loose enough to slip. There is a recent thread with a nice diagram on how to loosen the power steering pump and tighten the belt. A good purchase for a jeep owner is either a downloadable Factory Service Manual or at least a Haynes/Chilton book. All three give a detailed break down of how to tighten the belt and do a lot of other useful stuff. Here is the thread...

https://www.cherokeeforum.com/f2/tig...e-belt-210208/

 

Generally with a serpentine belt, you are going to want to see around 3/8" to 1/2" of deflection under thumb pressure across its longest span.

A belt tension gauge is cheap and a good thing to have around, but even though I have the gauge I still usually just use a string line and a 4R machinist's rule to get myself in the ballpark.

 

Loosen pulley under power steering pump a little..turn adjusting bolt 1/2 turn. Tighten pulley. Test. Repeat until squeal is gone.

Then, use a marking pen to mark adj bolt location and next time you take it off, count the number of turns required to loosen and leave it lined up on your mark. Tighten back the same amount of turns.