Recently the license plate lights and the backup light failed to work at all....so I had to fix whatever was wrong.
Ended up taking the inside trim/cover off the hatch and after testing a bunch of wires and connectors discovered that the problem was a broken ground wire...where it routes between the hatch and the body. This bundle of wires flexes each time the hatch is opened/shut....and....the ground wire is a LARGE white wire with a black stripe....so it has less flexibility than the other wires I'd guess.
So after a lot of testing and so forth I happened to pull on this wire and had it separate....basically cleaned a short bit of insulation on both ends...put them straight together and soldered them...covered by a length of shrink tubing and some vinyl tubing split and taped....over that.
So now all 3 lights act like they should. The wiper was never affected...must have a separate ground.
The cover inside the hatch is held on by some plastic screws that go into some 4 pronged holders that grip the sheet metal...plus some clips that just pry loose. If the screw/prong thingies bust...they sell black plastic generic type trim holders at the parts stores.
Inside of the hatch with the cover off...wiper motor on the right..and you can see the lock cylinder to the left of that in the middle of the dark area...with a rod going down (or up in this pic) to the latch.
There IS a switch inside the latch on the hatch that controls the dome light....found the sucker.
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Where the break in the ground wire was...AFTER the fix...the rubber grommets at the ends are espec important to keep the wires from shorting on sheet metal...this fix might be good for 20K or so?