When the '91 245 was new, we had two small children who had lots of friends and the third seat was up most of the time. That tailgate got opened many times a day. The original wires failed after about 6 years.

I took some spare wire out of my junk box and soldered in extensions to the wires down in the tailgate, then I pulled about 8" of fresh wire up through the hinges, cut the plugs off the bad section and resoldered them onto the freshly cut wire.

Total cost for repair - maybe $2 worth of solder and shrink tubing.

After a couple more years, the tailgate usage dropped off considerably, so I have never had to do it again, but I have enough slack in my extensions for one more repair like this. After that, if I still have the car, it will be due for fresh wire.