horse trailer wiring

[kyajazz]

Help! I have a horse trailer that I want to hook up to my truck. I can't figure out what wire is the electric brakes-I was told it had them, but there is no blue wire coming from the brake area, only red and brown. everything else is working good. are the red and brown wires only for brake lights? not the actual brakes?

 

[buck52]

more info is needed... the truck may or may not be setup for the electric brakes...

there are many options these days...

here's a link for you... http://www.etrailer.com/faq_wiring.aspx

a battery and couple of jumper wires will quickly tell you which wire accuates the brakes...if it has them...

 

[LauraMJ]

There is no separate wires for brake lights, those work through your signal light wires. Red and Brown wires are not factory wire colors in the truck, so do you mean the red and brown are coming off from behind the wheels of the trailer? If you are talking about the wires on the truck itself, then someone has obviously replaced them and that being the case, it may be hard to tell what they are for without experimenting with a wire tester to see what powers them.

but there is no blue wire coming from the brake area,

What do you mean, "brake area?" Do you mean the brake box in the truck? Or do you mean from behind the wheels on the trailer?

 

[metweek]

Does the truck have a brake controller like those pictured here http://www.etrailer.com/c-bc.htm or is the trailer braking system factory installed?

 

[kyajazz]

the red and brown are from the trailer end, they come right out of the hub of the front wheels (2 axle) so they must be for the brakes. every diagram I have looked at have blue wires for the brakes. the truck has a new controller and it is not registering when the trailer is connected which means that we have it wrong somehow. all of the other lights work....

 

[LauraMJ]

The blue wire comes out of the trailer PLUG and runs back to connect to BOTH red wires. The brown wires are grounds.

 

[LauraMJ]

If there is no blue wire to be seen anywhere, then start at the brake box in the truck and find the blue wire. Trace it back to a another colored wire that it might be spliced to (shouldn't be more than 8 or 10 inches back and then follow that wire back to the truck plug. Is there a corresponding color wire on the trailer brakes? I'm thinking that maybe someone replaced the blue wire for some reason and now it is another color.

Is there ANY other color wire other than the red and the brown ones coming out from the trailer brakes area?

 

[kyajazz]

those are the only wires coming from the brakes....
the blue wire from the controller *I think* changes to black.....but my black wire on the trailer is for the running lights.....
my mechanic left town for the winter it seems

 

[LauraMJ]

Okay, here we go........

You need to get up under the trailer.

The red wires coming from your trailer brake are should be twisted together at some point into one wire which travels to the trailer plug. The two brown wires are grounds and they should be bolted, or screwed, to the trailer's frame somewhere. Make sure those things are correct. When you trace the place where the red wires come together, they will be, at that point, connected onto a single wire that goes to your trailer plug. Make a note of the color of that wire. That SHOULD be your blue wire that you are looking for, however, it does not HAVE to be. ANY color wilre will work, so long as it is a 12 gauge wire. So, if it is NOT blue, don't worry, just look at the wire, note it's color, and check the wording on it to make sure it is a 12 gauge wire. Now, that wire goes into the trailer plug at the pole marked "S." Make sure that it does. If there is no wire connected from the TWO reds to the "S" pole on the plug, you will have to add that wire. Again, any color is fine, just make sure it is a 12 gauge wire.

Now, go up to the brake box in the truck, and trace your blue wire there. You said it is spliced into a black wire, you think. That is fine (again, so long as it is a 12 gauge), but you need to make sure, and then you need to follow it back to the truck plug. That wire (the color does not matter, so long as it IS the wire from the brake box) should go into the "S" pole on the truck plug, too.

That wire from your brake box feeds juice to the magnets that are in the trailer brake assembly. When that juice hits the magnets, they jam up against the sides of the brake drum and that causes the brake shoes to engage.

Now, here's something that is critically important. If the reason you are working on this is because you've previously pulled this trailer and suddenly the brakes are not working, the magnets themselves may no longer be any good. You MUST TAKE IT TO BE SERVICED!! The brakes will NOT work, at all, if the magnets are worn out. However, if you have never previously hooked to this trailer, then you MUST trace each pole coming out of the truck's plug (or use a tester light) to make sure that that is wired correctly. Here is how it should be connected to the plug:

Trailer brake box wire: "S" pole
Left turn signal: "LT" pole
Right turn signal: "RT" pole
Ground: "G" pole
Auxillary (for trailer interior lights--optional): "A"
Trailer Marker lights: "TM" pole

Do this even if someone has told you that the truck is wired correctly. A case in point, we just bought a new truck, hooked it up to our horse trailer, and upon hitting the right turn signal, the left TRAILER signal would flash, and upon hitting the left turn signal, the right TRAILER signal would flash. Someone had gotten the wires for the signal lights connected to the wrong poles. Obviously, if they were pulling a trailer, the trailer lights ALSO would have had to be wired backwards like that too. Unless they simply never noticed that their signal lights didn't match.........

Now, for the trailer plug, just do what I described earlier, make sure that the two red wires come together and that both are connected to a wire that runs into the "S" pole in the trailer plug, and that the two brown wires are attached to the frame of the trailer. If you have interior lights in the trailer, then the wire for them will run into the "A" pole. You say that the black wire on the TRAILER is the "running lights." If so, then that wire should be connected to the "TM" pole in the trailer plug.

Remember, it literally does not matter what the color of the wires are, but it does make things a lot less confusing if everyone uses the same colors. And for the individual, it is a lot less confusing if the same color wire is used for the same pole connection on each plug (so if you have to run a wire from the "S" pole on the trailer plug back to the two red magnet wires, use a black one to match the one that the trailer box wire is spliced onto, or use a blue one if that is easier to remember, since you already say you have a black wire for the trailer marker lights).

If you have any questions, let me know.

 

[JohnWill]

Laura should be the authority on horse trailers, you're in good hands.

 

[wacor]

Laura should be the authority on horse trailers, you're in good hands.

I agree

I am quite impressed.


But just to help a little Laura...............

Now, here's something that is critically important. If the reason you are working on this is because you've previously pulled this trailer and suddenly the brakes are not working, the magnets themselves may no longer be any good.

I believe it was indicated that this was a new hook up.

Help! I have a horse trailer that I want to hook up to my truck.

 

[LauraMJ]

I agree, wacor, but, I just wanted to be sure, because a lot of people don't realize that they are run by magnets that go bad........and there are a lot of reasons why this person could be wanting to hook this trailer up to another truck. I just wanted them to understand that bad magnets are sometimes an issue and that it's something to keep in mind if the brakes don't seem to be working properly.

I am quite impressed.

Thanks. Though I have to say my husband (who seems to have a working knowledge, if not expertise in pretty much all things that have wheels or is mechanical) has taught me everything I know. We've worked on and hooked up a LOT of horse trailers together, both ours and other people's.

 

[kyajazz]

to all, and especially Laura, thank you for your replies.
I think if we can't figure it out from what you told us we'll have to find another mechanic!
there is something to doing it on your own tho', besides saving money
I certainly would not take the chance that it weren't safe. I have had the trailer for just a month or so and have been working on the little things. after this is all figured out if the brakes seem to not be doing what they should mechanically I certainly will have it taken care of.
the story you told about the blinkers happened here too, if thats an indication of how things started. funny how it isn't just universal in how its all wired.
thanks again for all of your help. I will let you know how it goes

 

[kyajazz]

whoo hoo, its all set! brakes are running good
thanks so much for all of your help

 

[LauraMJ]

You're quite welcome, I'm glad it worked for you.