2003 Chrysler Town and Country A fairly loud whirling sound

With the hood up, listen & see if the noise sounds like it comeing from the alternator. The alternators on these have a clutch (decoupler) pulley on them and they are bad about going out. The alternators are fairly expensive to replace, but you can find just the pulley and someone who rebuilds alternators replace it for you. I was out about $60 for the pully & labor to replace it, of course I pulled the alternator my self.