I've got a 1992 Trans Am GTA that isn't blowing AC out the front-facing vents. Instead, all of the cold air keeps going out the windshield vents and floor vents. This happens on all settings between Low and High, as well as on Max, Norm, and Bi-Lev.

I was told by a friend that it may be a vacuum issue, but I don't have the slightest idea of where to start troubleshooting the problem. Has anyone had this problem before, or perhaps have some words of wisdom that can help me at least get started on fixing this?

 

Your friend is correct, it is a vacuum issue. first check the hard vacuum line coming out of the passenger side firewall. make sure it is connected to a vacuum source on the back side of the plenum and its not broken or leaking.

if the vacuum supply line checks out the problem will be in the vacuum switch in the climate controls above the radio.

 

Ok, I've checked the vacuum lines and they all seem to be in one piece without any holes or anything. I'm going to take a look at the vacuum switch today. Is there anything in particular I should be looking for to find a problem with the vacuum switch?

 

Hissing.

https://www.thirdgen.org/forums/inte...anent-fix.html

 

it's not always the switch, and when it is you can usually hear it leaking. you can put a mityvac on the line going to the controls from the engine side and test it's integrity. if it fails get up under the dash and check every connection. there's one near the driver's foot that has a tendency to get loose when someone has worked around there. trace the line and check them all.