So, have an issue or three.

Had mybtrailer hooked up. Had a short and the ground and 12V wires in the trailer melted. Blew a fuse in the truck.

now, when i turn my right turn signal on, my back lights flash (tail lights, license plate lights). Then just lights on, the right brake light is on, but left tail light is on. Left turn signal os normal.

then i realized the backup lights do not turn on.

but, if i plug the trailer in, the trailer lights work normal. But truck still has the problem
so, is this a wireing harness issue?

anh help or where to start?

 

Welcome to FTE!

To begin with, we need a better description of your truck such as model year, engine, drive train, any mods and the type of trailer you are pulling.

 

this is a 2016 Ford F150, 2.7 EcoBoost, 4wd. Ford just added the factory Trailer Brake controller.

the trailer is a cargo mate 14 ft enclosed with trailer brakes.

a canopy was added recently too. The canopy dealer used a wiring harness rhat plugs in live with the 7 way trailer connector.

 

Just a quick guess but I'm betting you have some melted wires on the truck side that are causing the problems. You are going to have to get under it and trace the wires out.

 

So just so you know on 15+ trucks you need a dedicated battery to run 12v accessory. The truck will not support it, lots of us have run a dedicated charge cable to the rear of the truck from the battery.

 

Well, have traced it down and found a whole harneness melted

 

That will do it. The question is whether the mod to the 7-pin was the cause of the short or not.

 

Not sure how the 7 pin trailer can affect the truck lights, since they are on two different circuits. Im thinking it is a coincidence, and thebtail lights shorted to the frame whete there was a sharp corner

 

looks like it actually affected wires all the way across the frame

 

Ouch! Sorry.

 

My SWAG would be you lost a ground in the meltdown of that harness, causing the weird failures. And then ground gets re-established through the trailer when you plug that in, and stuff starts to work correctly again?