Had my 06 300C at the dealer as when the a/c is on the vents in back of the console for the rear the air coming out of them is ambient. Not cold but same temp as outside. The dealer says this air is not controlled in that heat or a/c is not affected there. Does this make sense or is the dealer not telling the way it is.

 

sounds like BS to me . Mine works just fine .In fact my grand Daughter loves to put her feet up to the vent while the A/C is on . Shes got hot Feet

 

More air conditioned air is sent to the rear vents when you select "bi-level a/c." Some air makes its way to the back when you have dash upper vents on, but select upper and lower and you should get fully conditioned air in the rear.