Trailer brakes.

EWS · Dec 1, 2019

I am about to install electric brakes on my tandem axle trailer. I will need to change the trailer plug to a 7 pin. The truck is OEM wired for brakes with a 7 pin. The socket on the truck has a pin at 12v at 1 o?clock that is live while running. The pin for the brake at 7 o?clock is also live while running. Is this correct? This is with the brake pedal not pressed.

old · Dec 1, 2019

Yes likely to have to go with a 7 pin trailer plug. As for the places that have 12 volts when the brake pedal is pushed one should be for the brake lights on the trailer and one for the brake and NO they cannot be switch out. A new plug will come with instructions as to how to wire it up. Also the plug it self will have markings on it so if you understand there abbreviations you can hook up the wires as they need to be hooked up

HNM · Dec 1, 2019

I do not know what truck you have or how it is set up but I have never had one where there was power on the brake plug unless the brakes were applied.

ohiojim · Dec 1, 2019

i have an 09 silverado and the brake pin is hot all the time. it was explained to me that it is amps that apply the brakes, supplied by the controller. i'm no expert but that is what i was told.

Airborne · Dec 1, 2019

Check this out

https://www.etrailer.com/faq-wiring.aspx

JD Seller · Dec 1, 2019

What is throwing you is the brake terminal has low voltage on the pin for the controller to "sense" when you hook up to a trailer. It is just milliamps not enough to make the brakes apply. Here is a picture of the wiring diagram that new trailers/trucks have. Many of the plugs are marked for a different wiring combination so watch that when wiring.

David G · Dec 1, 2019

That is not correct, there are two configurations, that I think swap the brakes and the hot pins.

Stephen Newell · Dec 1, 2019

The trailer has it's own battery which engages the brake in the event the trailer is disconnected from the vehicle. The 12v line is to charge and maintain the trailer battery.

Steve@Advance · Dec 1, 2019

JD is correct, that is a sensing current to tell the controller there is a brake connection made.

It has to do with turning on the "OK" connection light and/or sensing a short.

Wire it per the diagram, it should work.

When wiring a trailer from scratch, I like to run a brake wire and designated ground wire to the center of the trailer between the axles, then branch from there with equal length brake and ground wires. That applies equal power to each brake.

Trailer wiring is exposed to some of the worst conditions, vibration, water, snags...

I use soldered connections with liquid tape and shrink tube, tie everything up, protect the wire as best as possible.

RCP · Dec 1, 2019

Be careful with the color codes on the trailer plug pigtail, they do not always follow convention.

Rich

JD Seller · Dec 1, 2019

David the two different configurations are on the six pin connectors. The auxiliary power and brake are switched. Hook up to a trailer wired the opposite way and the brakes are locked. I have not seen that on the seven pin/RV style plugs.

showcrop · Dec 2, 2019

Do you mean 6 flat with a pin in the center?

John T · Dec 2, 2019

In RV supply stores they sell what I call Horse Trailer 6 pin plugs/adaptors WITH TWO DIFFERENT CONFIGURATIONS regarding electric brakes and the 12 Volt auxiliary pins HOWEVER the 7 pole round RV plugs are one configuration with the Elec Brakes and 12 Volt Auxiliary. The one ALWAYS hot is 12 Volt Auxiliary.

John T
7 Pole Wiring

Trailer brakes.

EWS

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old

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HNM

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ohiojim

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Airborne

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JD Seller

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David G

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Stephen Newell

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Steve@Advance

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RCP

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JD Seller

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showcrop

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John T

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