I have a 2006 LJ that has just developed the common problem of lack of air flow control. All control positions result in air flowing through heater/defrost vents. I have looked for vacuum leaks and find none. The cruise control works. My guess is that the problem is in the switch. The blower control is fine, but the blower switch is fully operational with the system “off”. The ac/heater switch does not have solid clicks when switching functions. Could the function switch be the problem?