I just thought I would give a little back to this website that has given me so much info in the past. Someone out there might have the same question/problem.

I have a 97 MC, 3.1L, and the heater/AC air was only coming out of the defroster. Couldn't get anything out of the panel or lower floor vents. Figured it was something to do with vacuum. Eventually found it. It was a small vacuum hose that runs from the top passenger side of the intake over to the driver's side and comes to a tee. The tee evidently goes to the vent controls and to some sort of reservoir up in the front driver's side fender area. I must have damaged the line going forward when I changed out my battery a few months ago. I plugged it at the tee that goes forward to the reservoir and everything works fine now. I will make the proper fix later.

Cheers,

Steve

 

Vac leaks can be a troubleshooting nightmare... Glad you found the problem!!

 

... and for those with similar problems, you should know that most A/C controls operate that way. The problem is finding the vacuum leak. In a lot of cases, it happens after other repairs are done (just like changing the battery). A vacuum line left off or damaged will cause the air distribution system to go to the default position, which is either the defrost of the floor.

Hope this helps!

 

Thanx,Man I just purchased 95 monte w/3.1 engine my ac would only come out on the floor & defrost vents after I read what you found I went out & found that same vac line broke below the battery repaired it ac works perfectly out the ac vents thanx,so much,DUDE