First, thanks for the replies.
A few months ago I turned the a/c on and it would run cool for a short time then it would get hot. When I would turn the temp selection to cold the air was always heated, even if it was air from the outside vent. Basically the heater would stay on for a day or two blowing hot air even with the temp switch at the coldest position. After a few days the vent air would be the same temp as the outside air, meaning it wasnt running across the heater coils any more.
Per the dealer I have an actuator problem. From the info I have seen there are two doors with actuators, the one with the actuator on the passenger side near the floor which I think runs the recirculating air door, and the second which I think is somewhere behind the radio which runs the temperature/air blend door--this is the one I think has the problem, but I was kind of hoping for a confirmation before I start tearing the dash apart and risking breaking old plastic interior parts.
I should mention I am not a small person and I truly hate working under the dash.
Edit: I just did some more troubleshooting. I disconnected the recirculating door actuator (lower passenger side) and started the truck, turned on the a/c on cold. Nice cold air, so I went for a short drive; after a minute or so I heard a "thump" like a door closing, and the air immediately blew hot. I think it must be a weak air blend door actuator, a pita to get to of course. Oh well, might as well upgrade the stereo while i'm at it.
thanks again for your help, I'll post the info once I get it fixed, might help another poor soul with the same malfunction.