My 1999 jeep cherokee belt squeals very loud when giving it gas and chirps a little when idleing

BAD BELT OR BELT NOT TIGHT ENOUGH

how tight or lose is the belt. pull of the belt and spin the alternator and ac with out the belt to see if any noise

Your belt may be glazed over or loose also you may have a tentioner bearing going bad.A good visual check will help determine the cause.If you squirt the idler in the center with a little wd40 while it is chirping and the noise stops you will know the problem.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

you should probably take it back to him and make him fix it right. sounds like there is still a problem there

check your motor mounts. sounds as if one is broken or worn out, also, check the tranny mount.

Stop!
One of your pulleys is seizing. Most likely the a/c compressor or the tensioner (idler pulley).

Use a helper.... turn OFF a/c and have someone start the car. Observe the pulleys and see if the center one quits turning or is the source of the noise.
If can't determine and no noise, turn ON A/C and observe.
You will find it, but stay out of the line-of-fire if the belt breaks... it will be slingshot out of the engine compartment!!

one or more of the pulley's is defective, most likely the tensioner pulley, but check them all for wear and side to side movement which indicates a worn bearing, this causes the belt to not run true and chirp.

Try removing the belt and turning each pulley by hand. If everything is smooth and free, with the belt still off, drive down the block once and see if the noise is there (this will eliminate all rotating accessories on the front). If you hear the noise, then there is a problem deeper inside. Oil pressure is good? Dont' forget when doing this, you will have no power steering, so be careful.

Sounds like a vacuum leak. Check that all your vacuum lines are attached and in good condition.