I spent the day TS the 7 pin trailer hookup
And I made some interesting discoveries. After not getting any primary power and ground to the 7 pin I got out the factory manuals and did some digging. The wires were at the rear connector but DOA. According to the wiring diagrams there was supposed to be a three-wire power umbilical that originated at the front power box and went to the back. And there was also supposed to be an inline fuse assembly 12 inches from the firewall. After a bit of looking around I found no such thing. Now I know why it was dead. So where did the cable go?
This is where it got silly. I was rummaging around in the power box and managed to drop a relay down into the fender cavity. In my attempts to retrieve the relay I was reaching down into the fender area and low and behold I came up with a weatherproof fuse assembly attached to a 3 wire umbilical! And it appeared to be down there for a while. The missing power cable was no longer missing!
And a bonus find! I came up with what looked to be the 3-wire male end of a household extension cord! What? It turns out that it is the plug-in for the block mounted oil heater on the diesel. Apparently it was not used very often, if at all. Now it is up where it can be used if need be.
That cabling was the major 12 volt feed, electric brake feed and primary ground for the 7 pin connection. At some point for some unknown reason it was cut loose at the box. And dropped into the fender well area. After re-terminating the wiring and reattaching them where they belonged I had full power to the rear assembly! Isn’t that amazing! Not really but good.
With that done I can now finish up the setting of the cables going to the trailer connecter. I had previously purchased a replacement head for the factory cable that was a multi-tow hook up that has both the 4-pin and 7-pin hookups on one faceplate. It simply plugs into the factory connector in place of the factory port and sets in the same bracket. Lots more convenient than adapters.
Done! Done and Done!