Brake Controller in a 2001 Dodge Ram Pickup does not Recognize the Trailer

Updated 11/25/2013 | Published 11/23/2013

Question:

Totally stumped on this: My trailer lights and signals all work when I hook up to my truck, but the trailer brakes dont work. The controller light also does not come on. I connected the trailer to my Expedition, and the controller light came on proving that the trailer isnt the problem. I pressed the manual control on the Expedition and I can hear the trailer brakes actuate. I bought a new controller for my Dodge, thinking that was the problem. Controller light still does not come on when plugged in, but all lights still work on the trailer. I checked the voltage on all of the wires on the back of the controller, and they all seem to be getting the right voltage: black = 12 v, red = 12 v when pedal is pressed, white has continuity to ground, and blue gets about 12 v when the manual switch is pressed. I have traced the lines and dont see any breaks or bad inline fuses. I also recently installed a new female connector in the back near the license plate. The truck also has a factory female plug inside the bed. I plug the trailer plug into either one of them, and get the same results. It is a 2001 Dodge 2500 Cummins. Could it be the trailer relay is bad? The whole system worked last summer.

asked by: Rick

Expert Reply:

All of the symptoms you are describing lead me to believe there is a ground problem somewhere, even on the trailer. A weak ground connection can show up with some trucks and not others, we have seen it before. The first step I would take is to inspect all of the ground connections on your truck and your trailer. Inspect the grounds for the trailer connectors and the grounds at the brake assemblies for the brake magnets. Even if the grounds look good, I remove and clean them. If they look questionable, I would relocate them.

If all of the ground connections look good, test the pins at the trailer connectors on your truck for proper voltage. You are getting 12 volts on the blue wire from your brake controller, so we want to make sure that voltage is reaching the trailer connectors. Test the pins in the 5 o'clock position (see photo) for proper voltage.

If you have no power at the trailer connectors for the electric brake output from the brake controller, there would be a problem with the trailer wiring somewhere on the truck. If you do have power at the trailer connectors on the truck, there could be a possibility that the brake magnets on the trailer are going bad. Again, this issue can show up with some trucks and not others. Remove the hubs and drums and inspect the brake magnets in the brake assemblies. If you see any of the copper windings on the face of the magnet, it is time to replace the magnets. I have also attached an FAQ article on testing trailer brake magnets that you may find helpful as well.

If you are not able to locate the issue or come up with a solution after following these steps, let me know what you come up with and we can take further steps.

expert reply by: John H