i have an 89 convo too! and one of them have fallen off the tracks... i just wiggle it to get it back on and it goes back up or down... is it your switch? or can u hear it trying to go up and down...?
Did u check the fuse?
if u did already, i might unscrew your button pannel in your door, and check the harnesses and make sure everything is plugged in nicely. its only one screw.