[tomj76]

In my experience, a system that is low on refrigerant will give cold air in the rear while delivering "less cool" air in the front. It's due to the different methods of creating the temperature drop used in each of the evaporator paths.

However, I've also experienced malfunctioning blend doors causing hot air to blow from some vents. I would be sure to check that the blend doors are not the cause before addressing the a/c.