Make sure refrigerant is fully charged. Does it have dual climate control? Perhaps passenger side sensor is not working properly
Under the hood in front of the transmission dip stick is a vacuum line. If it is disconnected or split it will make the air vents not work. If that's not it check your fuses.
your blend door which cost about $1000-1500
== == There are three electronic actuators under the dash: one is for the defroser, one is for the bank of four passenger vents and one ( this is you) sends air to the two driver side vents, the two mid-dash vents and the two rear vents. Either this actuator is faulty, or there's a problem with the electrical delivery system; mainly, the whole climate control panel in your dash (dealer cost: about $700.00).
I just fixed a similar problem on my 95 LeSabre, got info from this website. http://www.imcool.com/articles/aircondition/fix_vacuum_line.htm
The Avalanche has dual controls for the air conditioning system. One control operates the driver side ac vents, and the other control operates the passenger side vents.
The vacuum supply line from the engine is disconnected or broken. When the vacuum supply is cut off the system defaults to the defrost mode.
Take off the top dash cover.. There are some screws by the defrost vents, take off the tri piece to find those. And then underneath there will have about five more. Look up where the gear shift is to find these ones. Once you remove the dash cover, you will see a red box on the passenger side.
There is a conduit with a fastener at the end. When I obtained my 2005 Buick LeSabre my rear air vents seemed to blow less than I had expected. After further inspection, I discovered that the conduit was not attached to the vent stack. So I played with it until I got it to slide into the vent stack and it seems to work as I would have expected at present.
that is the default mode for the hvac, check vacuum line on passenger side of motor, comes for the strut area over to motor, main vacuum hose for system, mine had come loose
The 1984 Buick uses vacuum lines to change air flow from defroster to ac vents. Check the entire vacuum system for leaks.
I don't directly know about a '92 Estate Wagon, but I have a '95 LeSabre, and you have to start by carefully prying up on the vents with a small screw driver to pop them out. Then take out the screws that you just uncovered. This should allow you to remove the black plastic trim piece that spans the whole dashboard. After that, you can get to the screws holding the radio in and just pull it out and unplug it. But like I said, I have a 95 LeSabre, not a 92 Estate, so it could be different, but I hope this helps a little!