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Ask Chris (aka- Moose) Your Own Question
Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 47330
Experience:  16 years experience
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2002 F-250: Super Duty..trailer brake..the factoty wiring harness

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I have a 2002 F-250 Super Duty that I put a trailer brake controler box on. The controller is new and I connected it with the factoty wiring harness to the factor port under the dash and color coated my wires. When I hooked up to my trailer, the brakes were locked up and I had to hotwire a positive wire to the trailer to move it. Any idea what is wrong?

Hello Travis,

Thanks for visiting us technicians here at Just Answer. I myself will do all I can to answer your question fully and understandable. If you need more assistance on this matter please just hit reply and do so. If this has solved or helped you understand the fix then my efforts can only be rewarded by hitting the green accept button. I welcome you to reply if needed, you can still reply even after hitting accept. Thanks Chris



Unless I have misread the question it seems like this is a trailer issue. You need 12 volt power on the DB wire to apply the trailer brakes, not to release the brakes. Have you double checked and verified the trailer brake control is getting the correct power and ground signals at the in cab connector.

Customer: replied 7 years ago.

The problem has to be on the truck, there is not poitive juice on the test light when I touched it to the truck plug but the brake controler does light up. Also, when I touched a positive truck wire to the Blue trailer wire, the brake released but the brakes won't work because the truck is not sending the info and I had to bypass the trailer controller to make it roll

Are you testing the truck harness on the dark blue wire with the brakes applied and the truck running?

Are all of these inputs correct at the controller


Have you done a ohme test o nthe DB wire from the controller to the 7 pin trailer connector.

Customer: replied 7 years ago.
Dark blue wire, yes pedals were pressed, no I don't think it was running when I tested it. It was running when I tried to pull the trailer up with everything hooked up origionally. Does the truck have to be running to test, if so I will check it out in the morning?
Yes you must have the key in run or the truck running to test it correctly for a power signal.
Customer: replied 7 years ago.
The key was on. Is there a way to hot wire it directly from the brake controller in the cab to the trailer plug, if so what color wire?
The DB wire is the only wire which carries the electric brake signal. If the ohm test shows resistance or open this means the wire is broken and you must find the short or overlay a new wire from the front to rear of the truck.
Customer: replied 7 years ago.
what color is the wire if I need to run a replacement wire from the brake controller to the trailer plug? Las question I promise.
Dark blue
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