It was easy to see that the tailgate wiring harnesses were both broken going into the '92 tailgate. The the bottom of the gate and the latch were so rusted that the previous owner had removed the catch at the bottom of the door opening. Seemed to make sense to replace the tailgate with one from the '87.

Intermittently I have an issue where the bulb out indicator and the rear window defroster switch will light up when I step on the brake. Taking my foot off the brake, the 3rd brake light stays on at the intensity of a taillight.

I replaced the tailgate wires on both sides with new Volvo harnesses. No difference. The wiring inside the tailgate looks like it goes where it should, i.e. it worked fine on the '87.

Unplugging the rear defroster and the wiper solves the problem. The wiper and heater are on seperate circuits and the power comes from different sides of the car. Any ideas what to look at next ?

Thanks

Greg