I've rewired both sides however I don't have notes on color codes.

I do remember that the left side had two wires for the defroster running down the tailgate's side channel. Plus the center brake light and I think the license plate lights.

After rewiring all that I found that the trouble was the ground wire that merely goes across the hinge. This is a necessity because the hinge doesn't provide full electrical continuity when the car hits bumps etc. My lights blinked and did odd things whenever it got jostled. That's why there's a ground strap going across the hinge. All tailgate items are grounded to the tailgate and via ground strap to the chassis.

I provided a new ground path. There are existing grounds at two screws (brassy plating) near center of tailgate. I ran one wire from each screw; up the two side channels and out the small holes at top. From there it loops to a new stainless sheet metal screw going sideways into the car's tailgate frame opening. That takes care of bridging the connection from door to chassis. The "loop" has a bit of extra length so you can open/close the tailgate.

Of course if you remove the hinges you can just refresh the original ground strap there. But I did the whole job without removing the hinges so this was my "easy" way of building a solid ground. That was 2-3 years ago now, did it on two cars about the same time, and no problems since.
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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.