Serpetine belt slips in the rain
 

On a 2007 Town and Country in the rain I loose PS, AC and Alternator as the belt slips. I've Changed the belt and tensioner with no help. What could be causing this?:confused:

Your next best renewal is the Alternator pulley as it looks like its became shinny smooth due too slipping too long. You can however roughen up the muli-faces on the pulley with emery paper but its said not too last long. I'm sure the PS (power Steering) uses another belt.

There are also a couple of other things to check for. Look towards the rear of the engine compartment and look for the wiper tray drain pipe, make sure its not dripping onto the serpentine belt. That was a problem with my girlfriends 2005 and it had me demented, just couldn't figure it out until I stood there one day with a hosepipe spraying water on the windshield.

As goggs said you want to roughen up the pulley face on the alternator but also hit the AC, power steering and most importantly the crank drive pulley. Its also worthwhile cleaning all the pulleys with isopropylene alcohol just to remove any residue!

On a 2007 Town and Country in the rain I loose PS, AC and Alternator as the belt slips. I've Changed the belt and tensioner with no help. What could be causing this?

Gates has a repair kit it comes with a new belt, idler pulley and tensioner maybe $175.00.
or you can check under the van to see if the splatter shield is still there.
i know the Gates way for me work out with know problems after i installed it.