Need help trouble shooting problem with trailer wiring

[anderson750]

Let me start out by saying up front that I am pretty much an idiot when it comes to electrical. I finally bit the bullet and re-wired my car trailer. I replaced the 7 pin plug and ran a new 7 strand wire to a 7 pin junction box. From there I ran brand new hot leads to all of the pig tails and soldered all connections. While at it, I also decided to change out all of the ligts for LED's. The first issue I am having is with that my trailer brakes are not working. I get no apparent output from my brake controller. However I know there is not a problem with the controller since everything works fine when I hook it up to my toy hauler. The next thing is that the lights only work when the trailer is attached to the truck. When I unhooked it from the ball, all the lights went out.


The only thing in this whole set up that is not new is the pig tails that connect to the lights. I have them grounded to the frame at each light. It is pretty obvioius that everything is grounding through the hitch/ball connection and I know the problem I am having is a grounding problem, but am not sure how to fix it.

 

[Chevycrew]

There should be a pin in the 7 way that is grounded to the frame.

 

[anderson750]

It is. In the 7 way junction box I have the ground from the plug hooked to the ground pin and then a wire that runs out to a frame ground.

 

[Chevycrew]

Does your other trailer work with the ball unhooked?

 

[anderson750]

Yes. It is a 5th wheel and I backed up to it tonight and hooked the plug up. It was not physically hooked to the truck. It appears for some reason that it is not completing a ground loop through the trailer but through the truck.

 

[Chevycrew]

Your sure everything is wired correctly in the plug? Sorry, but I have to ask.

 

[gijohn40]

Here is the wiring diagram that you should follow... you can find it on state trailer supply website under the technical library.
From what you are explaining your pigtail is not wired correctly... what you probably did was put the ground to the trailer brake supply which grounds it out... and possibly blew a fuse. My expedition had 4 fuses under the hood that one was the trailer brake and it was after the controller. They were tucked away all by themselves and hard to find...

 

[Gravy]

sounds like a ground issue to the trailer frame.

 

[gijohn40]

on your pigtail the brake and ground wires need to be reversed... you have them backwards....

 

[anderson750]

Thanks for the help. I will be digging back into this tonight. I hope it is as simple as the brake and ground being reversed, but I looked at it a dozen times the other night. But sometimes the more you look at it, the less you see. BTW, unless I have missed a fuse, there have not been any blown fuses.

 

[Caleb]

It seems if your having problems with trailer wiring, the most common place is ground problems. Where the lights come on when attaching to you truck, I'd definitely start there.

 

[anderson750]

It was definately a ground problem, but it did not have anything to do with any of the wiring. The flat pins on the truck connection had flattened out enough that they were not making good contact with the new trailer plug. A little bit of tweaking with a screwdriver and everything is working good.

 

[Herzog]

Sounds like you got it then. Seriously, every time I have wiring problems on the trailer, I just pull out the old stuff and run new wire because it seems to take a lot less time to do it that way with all random possible issues. That is after I've checked and cleaned the receptacle of course. Then if I still have problems I know for sure the wire isn't frayed somewhere and shorting out or whatever.

 

[Gravy]

Well glad it was easy.
When I rewired my trailer this summer, I drew a wiring diagram, laminated it and stuck it in the truck.
So now if I have an issue, it's easy to track down.

 

[anderson750]

Well glad it was easy.
When I rewired my trailer this summer, I drew a wiring diagram, laminated it and stuck it in the truck.
So now if I have an issue, it's easy to track down.

Easy fix but a complete PIA to figure out

 

[mbryson]

Seems like good tech to add to this thread if I’m ever searching again. I just snagged a cute little Big Bubba with someone that had “fixed” their harness. I need to check fuses in my truck but I think I have it licked after changing out the passenger rear trailer tail light. (Brake light was coming on with the marker lights once wired correctly—at least correctly according to the attached picture)



I bought a pigtail and box combo from Amazon. Mounted it to the trailer in a “safe” space, and started wiring.

Used this internet search to wire from. (I should compare to Jon’s PDF above if I’m ever doing trailer wiring again—we all know that’ll happen)




Checked trailer fuse 34 in the 2010 F350 engine compartment and…


..definitely not

passing current