What Trailer Wiring Do I Have?

[hashtagVanLife]

Any help on figuring out how to get my van wired for a trailer would be very appreciated.
I am think about getting a trailer soon and am trying to figure out what wiring my van has and what has to be added. I may want to install a brake controller. I have never done trailer wiring, but have wired speakers.
I bought my van at an impound auction last year so I have no info from any previous owners.
I think my van had the factory tow package.
There is a broken 7 pin round plug by the hitch.

Broken Plug

In the jack area there is what appears to be the trailer wiring all spliced together.

Wires Spliced

Color Code

There is also a small box with a plug going to that I have no idea what it is.

Mystery Box

Mystery Box 2

I I know I'll have to get a new 7 pin plug and splice it on.
How can I tell it I have the wires for a brake controller already at the plug?

[Lumpy]

I"m guessing your black box is a simple terminal box. Is there just the one, 7 wire connector on the bottom or are there other wires leading to that box? Are the 7 wires on that connector what's connected to the 7 pin round connector?


7 pin rounds -

I don't think I've EVER seen wire colors consistant from one vehicle to another. Especially with 3rd party add-on hitches. The guy at the local place uses whatever color wire he has. So I never try and rely on colors. BUT the positions of the terminals seem to be pretty reliable (but not always!)

Note that the colors on your label don't match the colors in that 7 pin flat connector.

Here's what SHOULD be standard 7 pin round -



A lot of times BRAKE is BLUE, but again not always.
A lot of times GROUND is WHITE, but again not always.

My GM schematic says that for a factory installed hitch, the wire colors "SHOULD" (emphasis mine) be -

BRN = tail, marker, lic plate lamp
YEL = L brake/turn lamp
DK GRN = R brake/turn lamp
WHI = GROUND
LT GRN = R B/U lamp
BLU = L B/U lamp

Note the absence of a BRAKE wire. My hitch was not designed for trailers with elec brakes.

The safest way, of course, is to install your own, new, 7 pin connector. Wire it with KNOWN signal sources (use your meter to test which lights to to what etc). You'll surely have to install your own brake controller. Those are usually very well documented.

There exists some very convenient "Trailer Wiring Cable" which is 7 color coded conductors in a jacketed cable. You can run the cable from cab to tail as a single piece of cable instead of messing with 7 individual wires. That's helpful even if you do decide to pull your stop/turn/tail and other lights off from their rear most sources.

Like any auto electrical project, do not overlook good ground. EVERYTHING in a trailer is based on chassis/frame ground. Trailers will "sort of" ground through the ball, but not reliably. Make sure your WHITE wire (if that's ground) is well grounded on both the vehicle side and the trailer side.


Lump - No Phone, No Pool, No Pets...King o' the Road

[CopperFiremist]

Mystery box is the Door lock relay I think

[hashtagVanLife]

Thanks for the info Lumpy and CopperFiremist.
I appreciate all the help I can get. Still learning.

There are no other wires going in or out of the Mystery Box. Maybe it is the relay for opening the rear door with the remote. I hadn't thought of that.

I will try to pull off the old connector and test which wire is which this week. I am heading into my work week tomorrow(I work 7 on/7 off).
I'll look up which brake controller to get, was poking around a forum a bit on that already.

If overtime cooperates I'm hoping to get a camping trailer before people store em for the winter.
Studded Tires became legal today, hard to deny winter is coming.

[Lumpy]

eTrailer.com is a great place for parts like controllers AND for a lot of good info. They have short video review/demonstrations of a lot of the parts. Good prices and fast ship. Tech support questions answered by real people at the actual place who actually know what they're talking about.


Lump

[Leeann_93]

Looks like standard GM 7 pin wiring harness to me. Blue is for the brake controller, orange is for a battery circuit.

[AstroWill]

Being as it is broken, the easiest would be to purchase the same type and move each wire over 1 at a time.

[hashtagVanLife]

Being as it is broken, the easiest would be to purchase the same type and move each wire over 1 at a time.

I'm glad I read that before I removed the old plug. It's one on those obvious things you usually think about too late.

[Lumpy]

Two things -

1) Don't assume that the wires in the back are connected to anything up front. Lots of cars and trucks I've worked on have a connector or terminal strip up front that those wires are connected to. But they're not connected to the appropriate points any further than that.

2) BE SAFE and as you remove a wire from the old connector, TEST it. Put a meter on it and turn on the lights or hit the brakes or whatever that wire is supposed to connect to. There's just no telling what some previous owner might have connected to some wire up front, thinking it was the right thing to do. Or what some trailer hitch installer might have wired up thinking it was the right thing. Automotive wire colors can be very goofy.


Lump

[hashtagVanLife]

I plan to use a meter on the wires as I go. Am I expecting to see 12v on each wire as I hit the brakes etc?

I don't take anything for granted on this van. It's had a hard life.
I certainly don't trust previous owners.
I got it an auction where it was impounded due to No License/No Insurance
While cleaning it I found an empty Spice package and empty little baggies that were for Meth, if you believe the Felon I asked.

[Lumpy]

I plan to use a meter on the wires as I go. Am I expecting to see 12v on each wire as I hit the brakes etc?

That can sometimes be confusing. Sometimes, in cars, you can see +12vdc on a lot of wires that should be OPEN. Likewise you can see +12vdc on wires that are "waiting for ground" like door pin switches. There may be almost no CURRENT available but there appears to be VOLTAGE because the circuit is connected to a current or ground source through some other resistive component, typically another light bulb. It's the mix of "Apply + voltage to power on" and "Apply GROUND to power on" that we have in cars that causes the confusing meter readings.

A simpler, and maybe more positive, way to check is with a test lamp. You can build one but they cost like two dollars in the "screwdriver with a pigtail" style that I just use the pre-made style. And if your test light has a long enough pigtail, you can take the light part of it into the driver's seat area with you while you apply brakes etc and you won't need a 2nd person to "OK NOW THE BRAKES!"


Lump