Trailer Wiring?

[Honest Bob]

Hey guys I'm wondering if anyone can identify or have any theory's on this wiring on my '75 GMC C35 2wd. I'm having a hard time identifying if it is oem and its purpose. I'm guessing its towing/cap related but I'm not an expert in that area.

Both the red and the green/white/black/darkgreen run from the engine bay and Y off right where the cab and bed meet and then continue to the rear bumper.

I dont seem to be getting any pixies out of any of the wires and I want to get a class V tow hitch and trailer wiring setup. I wouldnt mind reusing the wiring if I could as it seems like oem or somewhat professionally installed.

[trukman1]

I'm no expert but that last picture indicates to me it's definitely not OEM. Every time I've ever came across wiring with that fuse holder it's a PO add-on. As far as I know factory didn't use those fuse holders since all wires went through the fuse block. Only fusible links were the exception. Have no idea what it's for just pretty sure it isn't factory.

Good luck finding out what it is.

[Greenlee]

The last pic looks like a fusible link to me.

There are adapters you can buy for the trailer connector. That may be what’s in your first pic or that’s the spot where you plug it in. If the adapter is already there, you should have a pig tail coming out that plugs into the trailer wiring. They used to sell those adapters at just about any auto parts store. They probably still do unless these trucks are getting so old that they don’t stock them anymore.

[Greenlee]

I just realized that red wire may be a power wire for charging a camper battery or electric trailer brakes. The bigger 5 or 7 pin trailer connectors have connections for all that stuff. Could also be power for a bed mounted camper. Is there a trailer brake controller mounted under the dash?