I bought a 1991 Ford F250 that had a brake controller already installed. It made a mess of things and fried the wiring on both my truck and trailer. So what I did was go back and took out all non-factory wiring, I seemed to have fixed the problem. In my haste, I accidentally threw out part of the original wiring, but was able to get some of it back at a salvage yard. I tossed out a 3-wire connector that the brake controller was wired into that was actually factory original wiring. This wiring had labels on each wire (3 wires total) telling what each one was. I cannot find this factory original wiring harness for the trailer brake controller that still has the labels on the wire. It seems most of the 87-91 trucks didn't even have these 3 wires there, just a plug in the firewall, and the ones that did have the 3 wires are gone. My goal was to just get a brake controller and hook 3 of the wires up to these wires and the 4th to the ground.

The 3 wires are:
Blue
Red
Red with green stripe
These are unlabeled.

My brake controller has 4 wires. Blue=goes to brake, black=goes to battery, red=goes to stop light, white=ground.

I'm not positive which of the 3 original wires do what, since I don't have any labels. Any help here?

To further complicate things, I have the following instructions on the aftermarket brake controller I bought: For 1989-91 Ford F series trucks and vans with antilock brakes (which I apparently have) Do NOT connect to stoplight switch on these vehicles. Instead, go to a crescent shaped turn signal harness connector under the dash near steering colum. Splice red stoplight wire from brake controller to green wire on crescent shaped wiring harness.


I'm thinking this does not apply to me though because I should be using the factory provided wiring harnes??? IF I KNEW WHAT WIRE WENT WHERE! Now, I don't have a crescent shaped wiring harness under my dash. I have a rectangular shaped one. And the person who put the previous brake controller on before me cut into one of these wires and connected both ends into the brake controller, but it wasn't a green one, and when I went back and took out all the non-factory wiring, the truck wouldn't turn over unless I spliced back together this factory wiring they tapped into.

Any suggestions here?