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Testing the trailer plug

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Old Mar 24, 2009 | 10:36 AM
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Testing the trailer plug

So I am trying to work on the electric brakes on my equipment trailer, by using my truck.

I cant get the brakes on the trailer to work at all, but when I went to put a test light on the brake prong on the truck, and got the woman to step on teh brakes, there was no light.

As far as I know when she presses the pedal, it should send power to that prong, therefor lighting up the test light, but its not doing that. I towed a car trailer a month or so ago, and it was working fine. I have checked fuses, wires, and cleaned the actual prongs. I have a good ground on the test light, and the test light works.

Anyone have any ideas?
 
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Old Mar 24, 2009 | 10:41 AM
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Are using the factory harness/pigtail under the dash or one that was "wired in" to the brake controller? What kind of controller do you have?
 
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Old Mar 24, 2009 | 10:47 AM
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depending on the controller, when you plug the trailer in or if you touch the prong with the test tight it should light up the controller.
 
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Old Mar 24, 2009 | 11:01 AM
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The controller is a reese brakeman compact, it was in the truck when I bought the truck. I have no idea if it came stock or not!

Anyone have a diagram of which wire does what at the rear of the truck? Im thinking maybe Im not testing the right prong back there (although I have tested them all)
 
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Old Mar 24, 2009 | 11:06 AM
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My brake controller has a light that indicates "power" is on and increases in brightness as the brakes are applied. Some have a lever on the side to level the inertia switch inside and also a 'gain' control to adjust the "aggressiveness" of the braking.
 
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Old Mar 24, 2009 | 11:09 AM
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Maybe this will help: http://www.farmbox.com/shop/59
 
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Old Mar 24, 2009 | 11:17 AM
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Yeah roland this brake controller is the same. Has the "button" that you can push manually, and the light on it goes on when its working. I know how I have the trailer plug wired, but now Im second guessing if I have it incorrect for my truck. Easy enough to fix if I could get a diagram for which wire does what on the truck!

I am still puzzled though, I cant seem to get the test light to light up when trying to test the prongs at the back.
 
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Old Mar 24, 2009 | 11:25 AM
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Did you check the wires as shown in my link in post #6?
 
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Old Mar 24, 2009 | 11:33 AM
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I did yes thanks. I was hoping for one more ford specific though. Ive found a few different wiring diagrams for the trailers online, but so far none specific for our trucks.

For the record though, thats how I do have my trailer wired, was just kinda hoping for someone to say yep, thats how my plug is at the back of my truck, just so I can rule it out!.
 
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Old Mar 24, 2009 | 11:41 AM
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I have the factory installed 7 way trailer socket and that's how it is wired. Mine has the diagram on the outside flap over the socket. Did you or someone else install the socket on the truck or is it factory?
 
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Old Mar 24, 2009 | 11:50 AM
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The wireing on the trailer is not Brand specific. All trucks are wired the same, or you couldn't pull a trailer with different brand truck.
 
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Old Mar 28, 2009 | 02:09 PM
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i'm having issues also....what prong is for the trailer brakes, i dont have the cover.....
and i have a tekonsha envoy brake controller it was in there when i bought it, it looks like they used the factory harness, when it works, i can only use it manually, do you think they did something wrong or is the factory harness not setup for "automatic braking"
 
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Old Mar 28, 2009 | 03:34 PM
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How is the ground wire. Maybe check that see if it's tight & clean -Also are you gettin running lights on the trailor. Are they strong and bright?
 
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Old Mar 28, 2009 | 03:51 PM
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Sheldon,I had to go from the plugin forward to find power.I had a wire broke in a bend in the wiring harness.Take you time and do a section at a time to find power.

I know it suxs,just trying to help.
 
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Old Mar 29, 2009 | 01:16 PM
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mueckster that was a very good link for trailer wiring. I have wired dozens of trailer plugs on the trailers and on trucks(company I work for sells trailers). One thing you need to remember when looking at that link is that is showing the back side of the trailer plug or the front side of the truck plug (the outside under the door). Also when they first came out with is plug type it wasn't completely standardized. Some OEM would swap the 12V battery charge wire and the brake control wire. Meaning when you plugged your trailer in, you had a constanst 12V going to the brakes, so your brakes would be all the time. But now they have corrested that problem and it is as the link shows. Also the color codes are colors that they should be, but some truck and trailer mfg don't follow them so don't assume they are correct.

preppypyro, if your plug was wired from the factory, it should be wired as the link shows.

tnardo, they should come on when you press the brake pedal. Also, how is the controller mounted, becuse they have to be mounted correctyl to make the anertia braking to work correctly. The lower right hand prong is electric brakes on the truck.
 
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