One of the last annoying little problems to fix on this car is getting the dashboard AC outlets working. The AC itself is working fine and blows cold out the floor vent.

It was my understanding this is a vacuum control, and with quick peek under the dash I found the vacuum device that i think does the job. Basically right above the gas pedal. Hose goes from it to the heater-AC control.

Here is the strange part. With the car running and the AC blowing cold out the floor, I could reach up and actuate the lever coming off this thing back and forth by hand. It would stop the air blowing to the floor ... but never send air blowing out the dash.

The three dash outlets each have a local shutoff, but they were open. I tried all 3 AC positions (normal, recirc, etc.) but no change in behavior.

What am i missing here? Is there a second vacuum can or flapper or something I am overlooking?

 

What you appear to be missing is a Chassis Service Manual, specifically Volume 4, which covers the HVAC system.

There is only one vac diaphragm that operates the selector door that switches from floor to dash vents. When in upper mode, the air should flow out the maifold bolted to the rear of the heater case (the side away from the firewall). This manifold has three legs - one to each end of the dash and one up to the center vent. I'd suggest removing this manifold and looking at the selector door and vent tubes.

 

Correct - its a multi-manual set and so far I don't have my hands on it.
Well if no other actuator exists, I guess i do have to get a look at that door in there.

 

Vol 4 is on ebay right now for $8.95

 

Another thing to check is whether the vacuum is getting to the diaphragm. The A/C system is a vacuum hose nightmare, when I first got my car nothing worked right. I started checking under the hood and found at least 4 bad hoses and ultimately found leaks at the brake booster and trunk release switch as well. Once I actually had vacuum flowing to the system I found the selector buttons on the dash control were not working due to lack of use. I fixed mine by pushing them all multiple times, luckily they freed themselves up. If that doesn't work you may have to remove and clean / lubricate the dash control. Good luck.

 

If he's manually moving the lever arm for the selector door and still not getting flow from the vents, vacuum is irrelevant. That may still be a problem, but it isn't his primary problem.

 

^ agreed. Unless I'm not moving it all the way or something. This is a weird issue. I'd think their was a mouse nest or something blocking the manifold, but the car is super clean so it seems unlikely...
That's why I tossed it out to the forum, you never know what folks have ran into before. I've got to get into that AC manifold and see what's what.

 

Follow up. Manuals Acquired, problem solved.
The diaphragm over the gas pedal is for the defroster door, so I wan't doing a thing by messing with that. The one for the selector door is inside the unit, but after removing the manifold / AC log, you can see it.
Honestly I didn't need to do anything but track every hose, give them all a check, and move the selector door by hand a few times. Something got freed up, because it's working great now.
thanks

 

Well, it was minus fifteen here this morning so A/C won't be an issue 'til next summer!! On a similar note, the passenger heat has not worked for the past two winters on our .02 Bravada. then last week it started to work normally...Halelujah.