Sorry for the delay
Open the glovebox and empty it.
Lift up the glovebox a little with your knee and reach in with both hands and pull the rubber tabs (arrowed) toward you. I find its easiest to use one finger on each side and from the right side of the tab. This will allow the glovebox to open all the way
Once you have the glovebox open, the Airmix actuator is right there; unlike the Bonnevilles.
A quickie temporary fix is simply remove the actuator from the valve. its best to have the car already warmed up
mark where on (the threaded end of) the rod the white plastic retainer sits.
using needle nose pliers or something - Pop the plastic retainer up and out of the lever, rod and all.
swing the rod out so its pointing at you
rotate the head of the rod clockwise - off the airmix actuator arm and save the pieces for when you replace the actuator.
start the car and Adjust the metal valve lever that the white retainer was in so that it blows heat. (not the plastic one on the airmix actuator)
close up glovebox, just close it, the rubber tabs will fall slip back to where they should be without doing anything.
to replace the Airmix actuator, you might first want to remove the glovebox. there are 5 or 6 screws to remove a trim piece along the bottom (5.5mm?)
and then 4 screws at the glovebox hinge to take out. (5.5mm?)
disconnect the electrical connector on the right side.
undo the front bolt (4.5mm i think only 50% sure its been a few years now)
There is another one on the back, engine side of the module. You will need a thin socket/wrench to get that one out and you will be working by feel. Once you get the hang of it, its not bad. I pulled 5 or 6 of these out at the junkyard before I found a good one, all in under an hour. (from a 99 88 so I know its the same setup) and I didn't take off the glovebox and I'm a big guy.
Installation should be self evident.