How to Run the Trailer Brake Controller Output Wire on a 2004 Dodge Ram Truck Without Tow Package

Question:

i have a 2004 dodge 1500. it didnt come with trailer package. i want to add electric trailer brake,there is a plug under the park brake. i bought a p-3 controller. i hook it up and it work but can anyone tell me where the wire that come out of the harnass is.i traced it out of the fire wall and it green and i can put a test light on it and that is it. where does it go from there. help

asked by: leonard

Expert Reply:

The green 12 volt trailer brake feed wire you found is indeed the correct wire for running the power from the P3 brake controller to the back of the vehicle and connecting to the blue wire in a 7-Way adapter like part # 37185.

The green wire will be terminated in the wiring harness somewhere and is difficult to locate in many instances. If you are willing to explore the wiring harness at several locations, you will most likely be able to determine where the green wire has been terminated. Most likely it will be terminated near the spare tire at the rear end of the vehicle, but I have heard that it is sometimes terminated along the frame rail near the back of the truck cab.

Typically I do not recommend exploring the wiring harness in this way, because you could cause an issue with other wiring that is easily avoided by severing the green wire, and adding a separate dedicated trailer brake output wire, # 10-1-1. Add an appropriate length of this wire at the point where you found it outside the firewall and run it back and splice it to the appropriate wire on the 7-Way trailer connector.

expert reply by: Robert G