Have a '99 Chev silverado and there is a squeel from under the hood. Don't think it's the fan belt, but starting the truck is sluggish. Had to jump the battery this morning, now there is a "Burning wire smell". Any suggestions?

Possibly A/C or other component driven by belt(s) failing and causing belt to squeal due additional load or squeal from failed bearing in one of the components. Or just failed alternator causing low battery.

What about the belt tensioner?

Idler pulley bearing may be bad. Easy job to remove serpentine belt and replace pulley.

"Belt may falling flat and creating sash to squeal due extra load or squeal from came up short bearing in one of the segments."

Glad you have it fixed