I figured it out. There is in fact a trigger-type switch that operates the trunk/ rear dome light in wagons. The switch is just like the door switches and is located in the recess by the left tailgate hinge.

The torx screw holding the switch was pretty rusty. I gave the screwdriver a few taps with a hammer first to break the rust. Once the screw is removed, you can pull the switch. However, the length of wire connecting to the switch is too short to free the switch from the car. In order to get enough slack on the wire, you must loosen the plastic trim panel holding the trunk light to gain access to the left tailgate wiring harness in the roof (I removed the plastic fasteners on the left half as well as the dome light and let the panel hang down).

Locate the wiring harness in the roof and find the single white and black wire that passes through a black grommet. Push that wire through a few inches so you can pull the switch through on the other side. Disconnect the switch and clean all mating surfaces including the screw with a wire brush/ sandpaper and reassemble with dielectric grease. Clean the contacts on the dome light switch as well. Ensure that the switch works by testing with your finger and then put everything back the way it was. Enjoy your working courtesy trunk light.

Chris
'93 945T (214k)