Troubleshooting Trailer Brake Issues on 2004 Ford F-350

Updated 05/13/2019 | Published 05/12/2019

Products Featured in This Question

Pollak 7-Way to RV Socket LED Circuit Tester - Vehicle End

(159)

$41.89

Dielectric Grease for Electrical Connectors, 2 oz.

(1491)

$11.15

Hook Probe Circuit Tester

(66)

$12.94

Question:

Ok i have a 04 f350. 6.0 diesel. I thot my trailer break controller was bad so i replased it my issue is when im hooked to a trailer. With trailer breaks. My trail breaks stay ingaged all the time. And when my controller is pluged in my break lights stay on untill i unplug the controller. Im stumped no one can tell me how to fix it

asked by: Matt

Expert Reply:

It sounds like you have a wiring connection issue with your brake controller or a bad brake controller. When you plug in a trailer, your brake controller will see a power draw on your trailer brake circuit to tell the controller there is a trailer with brakes connected.

From what you wrote, it seems that your brake controller immediately sends braking power to the trailer when it senses connection. I recommend first cleaning your 7-way connections on your vehicle and trailer using sand paper or steel wool and then using dielectric grease # 11755 to keep moisture and corrosion out. Sometimes corrosion that is even difficult to see can cause a power jump from one blade to your brake controller output blade and that can cause what you are describing.

If that doesn't solve your issue, I recommend next using a circuit tester like # PTW2993 to check the red wire leading to your brake controller. This connection should only be hot when the brake pedal is pressed. If you get constant signal that is your issue. If you have a wiring harness, you will want to check the pinout to confirm it is the correct function. If you confirm that is correct and that red wire is getting power only when your brake pedal is switched, then I recommend cutting the blue wire coming from your controller back 6 inches from the controller. Use the circuit tester on that blue wire which should then make your brake controller read trailer connected. Hit your manual override on your brake controller and that light on the circuit tester should get brighter as you increase braking power. If it is always bright with no change when hitting the override, then your brake controller is bad and needs replaced. If the brake controller works properly at this point, then I recommend running a wire from that location back to your 7-way because there is a short on the previous wire. This will connect to the 5 o'clock position on your 7-way as shown in the attached photo.

expert reply by: Jason S