I have a 1996 Windstar 3.8L V6, manual A/C. To work on the engine I had to remove the cowl and what looks like the default fresh air inlet. The inlet has a vacuum valve and what looks like the vacuum reservoir mounted on it. They are just mounted there. The whole assembly mounts on the firewall on the left (passenger) side. I reinstalled it this week and I can only get air to come out the defrost vents inside.

It worked OK before I removed it. I never touched A/C. According to Ford manual this symptom means a vacuum leak. 1 vacuum line comes out of firewall and 1 line comes from motor. Both look OK and appear secure. There is another small "jumper" line. The valve has one inlet (larger) and what looks like 2 smaller outlets. The reservoir has 1 inlet. My guess was that motor line should connect to valve inlet. 1 valve outlet goes to vacuum reservoir via small jumper liner. The other outlet goes to line out of firewall.

Tried both combinations for what I believe are the 2 outlets on the valve, but maybe I have it all wrong.
These lines were not hard to remove so the removal should not have damaged them or connected components.

Can anybody give me some clues? Thanks.

 

It turns out I had everything hooked up properly. Today I tested valve, reservoir, and vacuum lines with a gauge. There is no vacuum leak. Vacuum source is OK so that means problem is one of the controls on the inside.

Did anybody ever troubleshoot the vacuum controller inside that feeds the vacuum motors or the selector switch (A/C, Max A/C, etc)? Any input appreciated.

 

I thought I would share the resolution of this problem. My van has the auxillary rear heating+a/c. The rear-auxillary control switch also uses the vacuum supply. This switch was leaking vacuum which affected everything in the main heating+a/c. With no vacuum, the main control defaults to defrost and heat or a/c cannot be selected. It gets worse. This control switch has been discontinued so I had to buy a used one. It did not leak so now the main control works. However, the switch won't supply vacuum to select heat or a/c in the rear. If you ever remove the climate panel and look at these switches you will know what I mean. So I got a/c up front, but I still don't have rear a/c.

 

i have this same, exact problem. I just ordered my new control switch in hopes that it solves the problem. if not, you pointed out one area i did not check. anyway, i called ford when i first noticed the problem and they told me to check the vacuum lines and if they were ok, it was most likely the control box. replacing the control box was a good move for you, and i hope it works for me. as far as the rear air goes... try this... in the middle seating, under the control switch is a removable wall panel. pull it off. there is a valve there that is controlled by vacuum. remove the screws that hold it in place. carefully disconnect the valve from the temp control arm. flip the control arm the opposite direction and you should have cold air coming from the sides as well as above. like i said, i have the same problem, and this idea is a good temp fix to get you through the summer. when mine went out, i had front a/c and rear floor heat. flip that rear control arm and you should be able to get cold air in the rear. if you need pics for reference, please let me know. good luck

edit: "new" control switch is also used, so i have my fingers crossed

 

Vacuum to rear A/C is controlled by the switch that also controls rear blower motor. My new switch didn't leak so the front vacuum worked, but rear vacuum didn't work like it was suppose to. Rear door needs vacuum for A/C. I took the 2 vacuum lines on the switch and jumpered them together with some vacuum parts I got at AutoZone. Now, the rear door always gets vacuum so it defaults to A/C instead of heat. I live in Memphis. Winters are fairly mild, but in the summer A/C is king for several months. When you move that rear control switch to the left, vacuum should be sent to the rear door but even my replacement switch didn't do that.

 

i think your vacuum line to the rear is toast. i would suggest the actuator isnt working, but you say it defaults to a/c, so it seems to be working fine. also, as far as i know, all the vacuum for that whole system should be controlled by the front dash. i believe the rear switch next to the middle seating is all electric and acts as a secondary controller for the rear fan speed. i got my "new" front/rear control for the front dash today and just installed it. Everything is fully functional. dash vents now work, and vacuum to the rear door arm has been restored, meaning i can alternate between hot/cold without manually flipping the stupid blend door. im excited about it too... i was worried that i was going to have to start from scratch under the hood, or beg someone for a bypass/jumper diagram to help me get through it. but, thats why i say im pretty sure its just a fan speed controller next to the middle seat. the front dash, rear hot/cold switch should be controlling that rear blend door. mine was fixed by replacing just that panel. if yours was tested and showed no faults, then i would say you have a problem running to the back.