I just bought this trailer:



It's a dual-axle 7,000 lb GVW with 7-pin electrical connector, which I have no experience with. I've hooked up a wiring harness for my truck, but the wire colors from my original 4-pin aren't used for the same thing as the same color wire on the 7-pin. I'm confused. Does anyone have experience with these? Here's a pic of the connector:



Also, I'm thinking of buying a Tekonsha Voyager brake controller; does anyone know anything about them?

 

so the trailer is already wired if so just buy a 4flat to a 7 round adapter

 

If you want to get the trailer brakes to work then you are going to have to wire in the correct plug. I believe the plug on your trailer is called an RV 7-pole or something like that. You can buy some kind of plug at Wal-Mart or any auto parts store to wire up to your truck. The package it comes in will say where all of the wires go. If you are going to tow that with your Toyota then you are going to want the trailer brakes for safety. Brakes are also required by law (at least in California anyway) for any trailers over a certain weight, I think it is 1500 or 2000 lbs.

 

I have the correct plug, wired according to the directions. I was just wondering why the brown wire on the flat plug has a different use than the brown wire on the 7-pole. This is how the 7 pole plug is supposed to be wired:

White: common ground
Blue: electric brake
Green: tail & license
Black: battery charg
Red: left stop & turn
Brown: right stop & turn
Yellow: center auxiliary

However, the 4-pin has NO red or yellow wires. Do I run an original wire from the fuse block for the yellow & another from the battery terminal for the battery charge?

 

I did a Yahoo search and it appears that the center is mainly used for backup lights and the battery charge goes to a power source, like the battery. See if that wire goes anywhere on the trailer side. I think it is used for recharging batteries in travel trailers, meaning you might not need it with your trailer. If you hook it up anyway, make sure that you put a fuse in the wire close to the battery.

 

Yes, it has an on-board battery for the electric brakes. It engages them if the trailer comes loose from the truck. I'm going to run the aux anyway in case I ever need to use it. Looks like I'll be busy running wire thru the truck this weekend! Thanks, supernerd!

 

You definitely want the brakes. I have a Tekonsha (pendulum style) controller. (I think it's the same style.) Installed it myself about 7 years ago, so don't remember which wires I connected to, but it seems like the brake light switch wire was one. The nice thing about the one that I have is that it detects changes in momentum and applies more or less braking force. You can also control the trailer brakes with a little lever on the front of the controller. Mounted it under the front center (stereo) console. Had to add a metal strap below the plastic pocket to support it. The little yellow LED on the controller tells you when you have a positive connection with the trailer brakes & turns red when the trailer brakes are being applied.

Once you've calibrated your controller, use some black electrical tape to cover the two dials to keep them from changing the settings accidentally.

In addition to a fuse for the charge line, you'll want a relay that is triggered off your engine running, so it doesn't pull down your battery when the engine isn't running. I forget which line I connected to (that was 15 yrs ago )

Your charge line & brake lines should probably be 10GA or better. Same for the ground.

 

One last question:

If I install TWO 14 gauge wires to the same ciruit, does that effectively give me a 7 gauge wire? Or does it not work cumulatively?

 

Splitting your wires like that could be dangerous if one takes more of the current than the other. The currnet will mostly go down the one with the least resistance, and that can change back and forth, it could start an induction current around the wires. It just is a bad idea, especially if one of the wires became loose, or broken, then you might melt the second, or cause a fire.

 

In direct response to your question:
For DC current, the impedance is directly proportional to the cross section area of the conductor. The area of the cross section is directly proportional to the radius (1/2 diameter) squared. The power loss to impedance which leads to heat build-up is thus directly proportional to 1/(radius squared), given a constant current. Of course there are a lot more factors involved, but that's the (somewhat) quick summary.

So you would have to have about four 14ga wires braided to equal about one 7 Ga.
HTH