I have not done it in a while but the process does not change. I usually go for the cheap fix if it is reliable and in this case it certainly is. This is what I wrote up some time ago.

Randy


I have repaired the wiring in the tailgates of the 240's three times. Each time I reused the harness on each side by simply splicing in about 12 inches of wire.
Start by removing the interior panel on the tail gate and locating the lower end of the one of the harnesses. Unplug each wire and cut each wire off about 2 inches from the end. Strip the wire, slip on a piece of heat shrink tubing and solder the 2 inch piece to the 12 inch splice then shrink the tubing. Do this for all the wires on that side. Then slip on another piece of heat shrink tubing and solder each new assembly to the CORRECT original wire in the harness and shrink that tubing. You now have a harness on one side that is 12 inches too long.
I do one side at a time without removing the tailgate. Some people like to remove the tailgate and lay it on a surface that won't scratch the finish. I don't want to wrestle with 75 pounds of tailgate. I rest the tailgate on a 4 foot stepladder after removing the gas struts. You can take one hinge loose at a time this way and complete one side before doing the other.
The headliner is removed at the corners to reveal the nuts that hold the hinges to the roof. Simply grasp the headliner at the corner, pull back and down and it begins to come loose. Notice how the rigid plastic sewn to the edge fits up into and behind the metel lip (very slick setup, easy to remove and replace). Loosen and remove the two fasteners on each half of the hinge (two on the roof side and two on the tailgate). Check your balance point on the ladder carefully as you remove the final fastners on the hinge to make sure the tailgate doesn't move too much and stress the ONE attachment point you still have.
Unplug the upper end of the harness and pull the wires up through the roof panel. There is one connector that is a tight fit. After you have all the wires pulled through and on the top of the roof you can pull the harness up and take up that extra 12 inches in length. Cut the connectors off of each wire (again leaving about 2 inches of wire on each one)and do the solder/heat
shrink routine just below the area where the wires were broken. Push the connectors back down through the roof and reattach them. Replace the hinge (try to leave a little extra slack in the harness in the hinge so as not to stress it any more than necessary when opening and closing the tailgate). I siliconed the area under the hinge to prevent leaks.
One side is completed at this point and the other side just involves doing it again. The first time I did it the total repair time was 3 hours. The second time only took 2 hours. The third time I didn’t watch the clock.

Good luck.