My 2006 Jeep Liberty has problems with intermittant AC airflow. Sometimes I have the AC on with normal airflow and then at random times the air will almost stop flowing from the vents (The air often stays cold too). The odd thing is that I will still hear the air flowing inside the system, it just won't be coming out the vents anymore. It's like some door within the system closes randomly. When I redirect the air through the floor vents, or defrost etc, I notice that the slight airflow changes to those settings yet fails to come out the vents except for a slight amount. What could this be?