# no horse trailer brakes



## rokjok (May 30, 2012)

I bought a 99 horse trailer and can't get the brakes working. It had a 6 prong round plug with the black wire on the 6 prong disconnected. I switched to a 7 prong round and had 'juice' at the wheels when I plugged it in to the truck. That was when I discovered the break away switch plunger was gone so I replaced that. Still not showing up on my controller. The controller worked fine when hooked to another trailer on the same day. Any suggestions?


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## Drabdr (Nov 26, 2007)

Hello, Rokjok! Welcome to the forum!

It seems that horse trailer wiring issues seem to be fairly common. Here are some threads here:

http://forums.techguy.org/do-yourself-projects/900682-horse-trailer-brakes-problem.html

http://forums.techguy.org/do-yourself-projects/862946-solved-trailer-light-problem-2007-a.html

http://forums.techguy.org/do-yourself-projects/644334-horse-trailer-wiring.html

http://forums.techguy.org/do-yourself-projects/548636-solved-need-help-wiring-trailer.html

It might be worth it to scroll through them and see if there is something that may be of assistance.

Just thinking out loud here... you stated it had a six prong, and switched to a 7 prong. Did you happen to "call out" the prongs on the six to see what they were for? Are you sure you matched them up to the appropriate prongs on the 7 prong?

If the controller works on other trailers, but not on trailer A; and if trailer A does not work properly on other trucks, then I would think you would want to focus on the trailer A wiring.


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## rokjok (May 30, 2012)

That was the simple version. I left the trailer plugged to the truck over night & went out find the truck batteries dead. Charged the batteries, rewired the 7 prong connector, worked on something else for an hour, came back and the truck battery was dead again. 
The trailer connector is marked white, red, black, brown, green, blue & whatever the center one is.
On the trailer there is white, black, red, yellow, brown & green.

White wire to white on connector
yellow wire to red gets left turn
brown wire to green gets tail
green wire to brown gets right turn
black wire to black makes the brakes lock up so black & red are now disconnected which means lights but still no brakes
Everything I've seen says black is 12v
I'm thinking maybe the brakes are black & red is 12v & by hooking the black to black on the connector I'm directly grounding the 12v from the truck?


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## LauraMJ (Mar 18, 2004)

> That was the simple version. I left the trailer plugged to the truck over night & went out find the truck batteries dead. Charged the batteries, rewired the 7 prong connector, worked on something else for an hour, came back and the truck battery was dead again.


You have a short somewhere........or do you have any lights in the trailer?


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## LauraMJ (Mar 18, 2004)

While I cannot think of how, at the moment, I suppose it's possible that incorrect wiring could be sucking juice somewhere constantly to kill the battery.......I mention it as a possibility because you are also saying you can't get the trailer brakes to work. Take a look at this post (link below) and see if this helps with regards to tracing the wiring and making sure it's all correct.



> I'm thinking maybe the brakes are black & red is 12v & by hooking the black to black on the connector I'm directly grounding the 12v from the truck?


Red is (supposed to be) the brake wire to the trailer....black is often the brake wire from the truck.

Seriously, though, read through this to make sure all your wiring is correct:

http://forums.techguy.org/5274718-post9.html


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## LauraMJ (Mar 18, 2004)

> brown wire to green gets tail


The brown wire should be the ground and should be attached to the frame of the trailer.


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## wowzer (Dec 28, 2009)

Agree with LauraMJ and Drabdr.

I have not worked on many horse trailers but have wired hundreds of 7 pole tractor trailer plugs and am not sure why they would be different but anyway it sounds like abad ground or a short. I have learned that in 12v wiring bad grounds are the source of many problems...

here a link for you...http://www.google.com/search?client=safari&rls=en&q=7+pole+trailer+plug+diagram&ie=UTF-8&oe=UTF-8


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## LauraMJ (Mar 18, 2004)

> I have learned that in 12v wiring bad grounds are the source of many problems...


:up:


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## Drabdr (Nov 26, 2007)

LauraMJ said:


> While I cannot think of how, at the moment, I suppose it's possible that incorrect wiring could be sucking juice somewhere constantly to kill the battery.......


Correct. Consider ohms law:
Volts= amps*resistance. So you have constant 12 volts, and you have amps,'then you must have resistance.

It may be a small amount so as to not blow a fuse, but constant so it drains the battery.

An effective ground is essential; and should theoretically go to the battery. But realistically the ground should be effectively
Grounded/ Attached (intimate) to the chassis; no paint underneath.


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## wowzer (Dec 28, 2009)

Drabdr said:


> Correct. Consider ohms law:
> Volts= amps*resistance. So you have constant 12 volts, and you have amps,'then you must have resistance.
> 
> It may be a small amount so as to not blow a fuse, but constant so it drains the battery.
> ...


Or to the correct corresponding pin on the plug.

http://www.etrailer.com/Merchant2/graphics/00000001/pics/q/u/qu363_2_800.jpg

Also if either has LED lights or a dual light setup ie: one light for stop and turn and a different light for turn, there may be a converter involved. and with LEDs the ground is opposite.


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## Drabdr (Nov 26, 2007)

wowzer said:


> Or to the correct corresponding pin on the plug.


Yes. :up: assuming the pin ground is of sufficient size.


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