Rear heat and A/C not switching

I have a 98 Windstar with 3.8L that has rear heat and A/C. Every year at the change of seasons (spring and fall) it takes a few tries to get it to switch over. This year, no matter what I do, it just keeps blowing heat in the back instead of A/C, regardless of where any of the dials are turned to. Any idea where the door is or what ever causes either hot or cold air to come out? Anyone else ever had this problem? Thank you.

I had the same problem with my 96, turned out to be the switch in the front console that controls the rear A/C. It's not only an electrical switch but it switches the vcccunm to the rear unit.

Untill I replaced the switch after checking that i had vac on 1 of the lines I hooked the vac lines together and the rear unit switched to the upper vents and A/C.

The switch is easy to replace and is avaiable from most online supplyers

I had the same problem on my 96, it too was the temp control up front.

Bob

Thanks again, the switch took care of it. I bought it from the local dealer. Ford part number F68Z-19986-AA, Motorcraft part number YH-1465, paid $38.70, $40.84 with tax. Took fifteen minutes to install; works great now. Thank you.