[jwholden]

I'm switching over to the newer style RV trailer connector in my pickup truck and thought I had labelled the wires correctly before cutting them to install the new connector. Unfortunately, I goofed.

I have a Reese brake controller that is connected to the wiring of the truck with the factory supplied add on harness.

How do I know I have found the ground wire at the back of the truck???

I have narrowed it down to what I think is one of two black wires.

Why do I have a circuit that shows it has 12 volts flowing through it but it doesn't light up the continuity tester???

This is a circuit between what I think is my ground and what I think is my brakes. I'm betting my guess here is wrong.

Any tips on diagnosing wires, especially how to be 100% sure which one is the ground, would be appreciated.

[Bill Schwab]

Most trailer grounds are white, John and you can just find a place where you can crimp a loop end down, and screw the ground directly to the frame, bumper, etc. Make sure the surface is clean and use some dilectric grease on the ends. Do you have a good bulb in the continuity tester, and how are the connections on it?
And is the ground tight and on a clean spot on the truck?

What brand and year is your truck? They have most of those things dialed in to the point where all you need do is buy a harness at the parts store, slip it between the tailight wires, and you are good to go, unlike the old days where we would hunt under a car for the wires to connect the loom.

[nebbe]

Do you have 6 wires or 7 at the back end of the truck? Have you been able to pull out your running lights, RT and LT? Then with your tester on 12 V DC, you can determine your 12 V constant if you have it. Then have some one in the truck push on the breaks and check each pole for power. The brake control wire will spike up and down on the volt meter as they put their foot on and off of the break. OH by the way why are you going to a 7 wire RV Style plug?

[jwholden]

The truck is an '02 Dodge quadcab with the Cummins.

There is no white ground wire at the trailer plug that came with the towing package. I connected my brake controller with the 'thingy' with four wires that came with the truck.

I have had no problem finding the turn signals and running lights, and assumed that the brakes were the blue wire at the back. But the results have me thinking I may have messed up on which wire is the ground.

The continuity tester works on all circuits when it is supposed to except when I go from what I think are the brakes to the ground. NO LIGHT.

If I connect what I think are the brakes to the left turn signal, lights etc when they are turned off I get a light.

I was reading the directions in the manual for my electric brakes and it seems you are not supposed to connect your brake wires directly to the negative battery cable. Which is what I am doing when using the continuity tester. Needless to say I'm confused and destined to waste a lot of time on this endevour. But I'm bound to learn something!

I am switching to the RV style connector because I am tired of breaking pins in the other style and it looks like a much sturdier connection. It seemed like a good off season project.

[Bill Schwab]

John: Is there a way that you can charge the wire(s) that are not connected to something already? If you can then all you need do is use the test light to find the ground...But as I said before, you can ground the trailer to its frame, and ground the plud to the trucks frame. When the ball touches to hitch, the circut is completed. At that point, if you have running, brake, and turn signals, if one wire is not connected, it wont matter as long as the other stuff is grounded.

[jwholden]

Just took the wife out to the truck and I have continuity on the circuit that is the brakes now. I suspect I was overanxious. I'll try again tommorow and test the volts and see if they spike or stay constant when the brakes are pressed.

I wonder if my finger bumping one of the other prongs on the trailer plug is causing me to complete a different circuit when testing for volts causing a reading of volts when the brakes aren't beeing pressed...

[nebbe]

In a 6 way plug that was a factory or proffessional installation you will have one wire that is a constant 12 volts. Whan holding your volt meter to the break wire and then sliding the slide on the controller you will see the needle raise the 12 v, that is how you apply more brake force.

Slide alittle = small amount of power to bakes -- 3-6 volts
Slide alot = larger amount of power to brakes -- 7-12 vots

I have had trailer problems as long as I have owned them. Our biggest problems -- 1) Salt 2) Salt 3)employees driving away without detaching the plug 4) or pinching the wires.

Broke down last year and purchased a Trailer Doctor from Hoppy for both the trailer side and vehicle side. It was worth the investment.

Another tid bit -- Soldier the ends of the wires before you connect them to the plug, a mechanic told me about this trick and it works well.

[GLAN]

does this help?

http://www.accessconnect.com/trailer_wiring_diagram.htm

http://www.marksrv.com/wiring.htm

[Bill Schwab]

The best way to stop salt problems is by using a 6 or 7 terminal junction box that semi trailers use. You can get them at any truck parts supplier. Then you run a 7 strand, 12 guage cable from the back all the way to the front to eliminate corrosion. Each individual wire is coated, and then they are wrapped and cased in a flexible polymer. Since the open wires are in a sealed junction box, and the rest is wrapped up, the only problems you will ever have if if some select individual under your employ forgets to disconnect the plug and drives off.

[jwholden]

Glan,

Those two links were helpful. One of them told me that Dodge ground wires are black. Unfortunately, I have two black wires at the back of the truck. Next step is to try switching those two, if no luck there I'll get some white wire and make my own ground.

Why in Gods name would the engineers mess with something so obvious as keeping the ground white??? It just seems silly.

I have a solder pot for my landscape lighting installs, it is awsome for soldering the ends of trailer wires before hooking them up.

[Bill Schwab]

John:

It is not so much the engineers, it is auto makers insistance on hiring factory workers who are not required to have scruples because the union thinks for them. The engineers took that into account, and, spec that every wire in a car is of a different color so they can trace them down if there is a problem. And, every car/truck has a different color code. The later was not too bright.

I have a friend back home who can crawl under a 55 Chevy and wire it, headlight to tailight to underdash in an 8 hour day. When he researched all the whys of color coding, that is what he was told.

[jwholden]

OK, I think the problem, or lack therof comes down to the difference between Volts and Amps.

When I test the VOLTS at the blue wire coming out of the brake controller I get about 11 with no brakes applied. I get the same reading at the back of the truck with no brakes applied. If I attach my continuity tester to the blue wire that reads 11 VOLTS I still get no light.

If I hit the brakes the continuity tester lights.

Is the Voltage in an electric braking system a constant at around 11 or 12 and I should only be checking for a change in amps, or that the continuity tester lights?

If the volts are supposed to vary I suspect I have a bum controller, though there was no error message on it. The acid test will be to hook up my trailer and see if the brakes work, but they havn't been there for me in a while so I'm trying to systematly make sure things are right from the start.

[Bill Schwab]

Do you have the engine running or not? Reason being...Think about LV lighting...For every foot you run wire, the voltage drops, and that is from a constant power source. On a vehicle, you draw from a stored source such as a set of batteries.

And, even at 11 volts, your light should light, just not as bright....

[jwholden]

Bill the 11 volts was with the vehicle off, I'm sure it went up a touch when the truck was started. I'm hoping that the REESE BRAKEMAN DIGITAL brake controller has some crazy stuff in the box to control the flow of amps when the brakes are hit. I checked my other truck and got the exact same results regarding volts and continuity.

The good new, I learned a lot about how my trucks are wired. The bad news, until I check out my trailers brakes I don't know if I achieved success.

There was a technical question phone number on the directions for the brake controller, I'll be giving them a call on Monday.

[site]

I fooled around with trailer wiring a few times for a half day each time. Eventually I figured out that it was cheaper to drive it three miles up the road and get the kid who does it all day every day to square it away in about ten minutes. He charges $35 for that ten minutes, but if it buys 3 or 4 hours of time for me it's worth it.