I have a 2007 Expedition XL XLT 2WD. The A/C and heat works fine up front, and the A/C works great in the rear, however, when you turn the rear air from cool to warm the air flow shuts off on the rear vents. I have replaced and checked the blend door actuators, to verify they work, no clicking sounds. The blower motor is working just no air flow thru the rear vents when on hot but when you turn it back to cool temp it start blowing again. Now with my back passenger side panel off I can watch the door blend actuators both turn when you go from cool to heat and from heat to cool. It's like they open the doors for cold air but close the doors to the vents for the heater to blow through.