ACC (automatic climate control) is the guts behind the zebrano fascia in the center console. Remove the wood trim, remove the screws (4, I think, but maybe 6). Gently slide the unit out of the dash and begin to look and listen. But, I would check under the hood first to make sure all the vacuum lines are in place and intact. Do the simple stuff first..
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.