Trailer Brake Wiring Diagram

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Apr 10, 2004
Ok, so I just bought a used car hauler a little while back and it is looking like the trailer brakes don't work as of yet. I was hoping somone may have a wiring diagram. I really have no idea what the system consists of on the trailer itself. I haven't had time to look into it and it would be sweet to know how it should be before I jump in.

I rewired my truck last night that the PO did a piss poor job of and it now looks like everything thing works: hook ground to blue controller turns on, put test light between the two, hit the brake, test light lights up.

Any help would be sweet
Typical trailer wiring:

Green - right rear turn signal
Yellow - left rear turn signal
Brown - Tail lights/marker lights
White - ground

Blue - electric brake
Red - auxiliary
yeah I know all that stuff, I've decided that i'm just dumb, or at least this is a dumb question if it hasn't warranted any answer. I guess the real question is, dose blue just run directly to the brakes with no other outside mechanism? My thoughts were that black (12V constant) powered the brakes and that blue was just the control system so to speak and that maybe there is some sort of control box. I must just be thinking to hard and my guess is that everything just runs to the axle. I suppose I will just look at it tomorrow and hopefully just discover a broken wire or bad ground.
Sorry, misunderstood your question - blue and white should go to your brake. White is ground, blue is energized from the controller and activates brake.

Black would be a constant hot - doesn't usally go to brake.

Does this help? or am I making it worse?

Silly question, but you are running a brake controller right? This is typically cab mounted.

Yep that is all I needed to know. This diagram had me confused because in the article that it came from it hints at black being part of the brake circuit. Which I couldn't digress whether that was true or not.


Silly question, but you are running a brake controller right? This is typically cab mounted.


Yeah my truck came with one but it wasn't working when I isolated the truck by itself, I have since rewired the truck and now it functions as it should. Now I have to rewire the trailer, not exactly what my weekend plans were supposed to entail. Hopefully the brake solenoids are ok.

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