1999 Chrysler Town and Country serpentine belt

Finally someone got it right. You asked why the problem wasn't there for the last 125,000 miles. That's proof you don't need to modify anything. There was a modification kit for vehicles where snow could get impacted near the right strut and knock the belt off. That involved adding a plastic shield but I can't remember if that applied to the '95 and older vans or the redesigned '96 and newer ones. I have a '95 with the identical 3.3L engine, and I live in the middle of miserable snow country, and have never needed that modification.

What the person meant by the pulleys is one of them is tipped or turned. Normally that sets up a horrendous squeal as the belt is forced to slide across it as it goes around it. The place to start looking is by sighting down along all of the pulleys to see if the belt is peeking out to the side on any one of them by as little as 1/16" in relation to all the other pulleys. The tensioner pulley is the most common cause because wear develops around the pivot bolt that allows it to turn, but the next likely suspect is the idler pulley. Usually you'll hear it buzzing if it has a bad bearing. The alternator and power steering pump don't usually cause this because there would be a lot of previous warning from noise. Look at the crankshaft pulley too. I can't remember if the pulley is cast as part of the vibration damper or if it's bolted on separately, but the bonding material between the center hub and the outer steel ring can let go. That will make noise too but before it gets bad enough for that, the only symptom might be the belt coming off.