I have a 2008 Caravan. The air conditioning works great up front, but will not blow out any cold air in the back. The heat doesn't work either in the back. We tried the controls up-front and in the rear. When you turn the ***** nothing happens (no sound no air). Where should be start?

 

Welcome to DF
If the controls are working, you could have a problem with either the mode door or blend door.Also should have the a/c system ck'ed for codes.