AC problem

Hello, I own an 89 GP and mine was doing the same thing. I'm not sure if the 89 and 92 models are the same but, what I found is, behind the ac/heater module, there is a vacuum adapter that controls where the air is to be distributed. Possibly, one of the vacuum lines may have come off do to vibration. If not, you can buy a new adapter for less than $20.00 at any parts store.