As the title implies, that is my problem. Can't get the AC to come out of anywhere other than the windshield defrost vents. Y'all ever encountered this before?

 

The h.v.a.c controls use vacuum to operate , does you vacuum pump work? Or does it leak ?

 

Like lpzd said you have a vacuum pump not working or a vacuum leak. The HVAC uses vacuum to move the baffles and doors to direct air. Here's a diagram to help you out. Most common place to look is the hoses going to the 4x4 locking hubs on the front wheels if you have the auto system.
The vacuum pump is under the hood on the right side. When you turn the key on you should hear it running

 

There is a solenoid near the vacuum pump that could be bad.

BBD

 

Once again FTE saved the day, the truck had rotted vacuum lines at the hubs, just plugged the two inlets with screws and using that as a temporary fix until I install new vacuum lines. It'll still blow out the defrost vents but after the vacuum pump shuts off it works normal. I was dumb for not searching previous posts on this topic, but thanks a bunch for the input provided.

 

Bringing up an old thread as I am in the same boat. Picked up a 02 4x4 7.3 Excursion Limited yesterday and the AC only blows out of the exhaust. Previous owner says it was working fine before his radio was stolen. Is there a vacuum line behind the radio that could have gotten disconnected or damaged when the radio was stolen or the new one was installed? Thanks

 

When my AC blew only out the defroster vents, I could find no leaky/missing hoses, and bought a new vacuum pump (Rock Auto) and that fixed it for the last 6 years. I wish I knew what the problem really was (the old vacuum pump seemed to work fine), but if a new vacuum pump can overcome it, that works for me. A crude fix, but it worked.

 

There are some vacuum lines back there, below the radio, attached to your HVAC control panel. I have my 2001 F350 dash apart to do some cleaning/repair and snapped these pics. You could take your HVAC controls out and have a look around there. Pretty easy disassembly process to get to it.



You can plug off the 4x4 hub vacuum lines to eliminate them as the source of the vacuum leak, if all looks good in the radio area, as your next troubleshooting step.

 

Thanks for the replies. So I looked for leaks and did not find any. I also changed out the 4WD Hub Locking Solenoid since it was only $40 so I could rule it out but that didnt fix the issue. The thing that puzzles me is that when I unplugged the lines to the solenoid the pump kicks on. I hook them back up and it runs until it gets to whatever pressure and then it shuts off at and then stays off. If there were a leak, I would think it would just keep running. Am I wrong in this logic?

 

Still fighting this issue

 

Is the pump creating vaccum? It might be running but not creating vaccum

 

Knuckle seals are a common point of failure. Did you test the knuckle/unit bearing/hub assembly for vacuum leaks?

 

I think I have it traced out. I pulled the AC control out and pulled a vacuum on each line individually. The grey line would not let me pull a vacuum. I followed it and found a crack in the line under the hood. I am going to replace it but not sure if I need to try to find the same rigid plastic type line or just use another rubber vacuum hose.

 

I got the grey line (under the hood) fixed and now I can pull a vacuum on it and it holds, but its still not blowing out the vents when I hook everything back up. I can pull a vacuum on the red line at the head and it will blow out the vents. Now I am wondering if it is pulling enough vacuum for the system. I am showing its at 15 in HG. Not sure where it should be but I would think it would be more than 15???

 

maybe a bad control panel? I think i remember my system only pulling about 10 and it works fine.