The switch is inside the latch mechanism itself. Pull the hatch inner panel off (two screws and a bunch of push thingies). Inside you will see a wire that goes to the latch, that is actually the switch. You may have to clean it up real good. I tried that, didn't work for me. Ended up being the wire inside the loom that goes to the hatch was broken, right at the point where it bends (read stress point). I had to fish another wire though the loom and replace it.
Also, if you ahve the switch on the lamp itself (push button switch) that will diable the interior lamps when the hatch is open (and only controls the hatch switch). That switch can fail, happened to me as well. I replaced it with a small rocker style switch about the same size that I found at Kragen.
Sequoia
(By the way, I am assuming that this circuit is about the same as it was in 1989)