Questions on trailer wiring

[redhat]

I am rewiring a 18' 7k landscaping trailer. The wiring has been apart before I had it. Wondering if you all might be able to shed some light on a few questions I have.

On the 7-way "to-vehicle" plug, I have 6 wires. Green, yellow, brown all make sense to me. I am going to assume red, white and black are 12V+, Trailer Brakes and ground. This is easy to figure out as I'll just connect it to the truck and use a test light or multimeter to see what is what.

On the trailer wiring side, I have a frame ground, also white, that makes sense to me. I have again, yellow, green and brown, signals and running lights. That makes sense. That leaves me with a black and white. I know the lights/signals will ground through the chassis. Do trailer brakes normally have a dedicated hot and ground lead? If so, that then makes sense and I have an idea on how to wire this.

I also have a breakaway switch and box, but that has a diagram on it, which makes sense and the priciple of a breakaway switch is easy. Normally open, when pulled it is closed and applies brakes.

 

[mk378]

Yes brakes have two wires to each wheel, brake hot (blue from the truck) and ground. All the wheels are wired in parallel. The polarity of connecting hot and ground to the two wires on the brake magnet does not matter.

The break away system energizes the blue wire from a battery on the trailer should the trailer completely detach from the truck. Pulling the pin out of the break away switch closes the circuit from the battery to the brakes. While driving normally, the "always hot" wire from the truck keeps the battery charged.

The best installation also has a dedicated ground wire to each light rather than relying on conduction through the trailer frame. Those connections often fail from rust.

 

[JohnnyG]

It tells you right there on the breakaway kit drawing that the black is 12V + from the vehicle (likely to charge battery) and White is Vehicle ground. Blue is the control wire to apply the brakes.

 

[tmorris1]

Connect appropriately to what comes from the vehicle.

7 Way Diagram - AJ's Truck & Trailer Center

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[55hambone]

The best installation also has a dedicated ground wire to each light rather than relying on conduction through the trailer frame. Those connections often fail from rust.

This little bit of time and effort will save you so much trouble in the future.

 

[redhat]

Yes brakes have two wires to each wheel, brake hot (blue from the truck) and ground. All the wheels are wired in parallel. The polarity of connecting hot and ground to the two wires on the brake magnet does not matter.

The break away system energizes the blue wire from a battery on the trailer should the trailer completely detach from the truck. Pulling the pin out of the break away switch closes the circuit from the battery to the brakes. While driving normally, the "always hot" wire from the truck keeps the battery charged.

The best installation also has a dedicated ground wire to each light rather than relying on conduction through the trailer frame. Those connections often fail from rust.

Thank you, this helps a lot. Also I just realized how dumb I am, I can just hop under the trailer and look at the wires going to the brakes

 

[rlaggren]

Pic #2 above shows a wire with a ring terminal (good) and a wire passing through a hole in the chassis w/out any protection (bad). Grommets are always in good taste and you can split them and install after the fact if that is needed. Chafe is one of the most over looked fail paths in any fabrication. That and metal fatigue. Strap, strap, strap...

I consider it more than worth it to get a decent set of ratcheting crimpers for installing wire terminals and use them on good terminals. Good = tinned with adhesive heat shrink tubing. And just as worthwhile is using good brand "marine" tinned wire. I may be bigoted, but I HATE redoing work that fails due to installation issues.

Here is the deep and dirty from a horses mouth. The guy has a severe love of talking about his work, but bear with him and you will come away with a good idea of the issues and methods involved in reliable low voltage wiring.
Marine Wire Termination - Marine How To

Regards,
Rufus

 

[D60]

At the risk of stating the obvious, watch out for RV vs Trailer wiring layouts in 7-pin

Although your colors don't fit either scheme.......

 

[Donald]

Look at Ancor wire and crimp connectors. The best marine ones out there. And crimping tools. West Marine and other places.