Troubleshooting No Power on Blue Wire After Installing Curt Discovery Brake Controller

Updated 05/21/2019 | Published 05/19/2019

Products Featured in This Question

Curt Discovery NEXT Trailer Brake Controller - Up to 4 Axles - Time Delayed

(56)

$108.95

Universal Wiring Adapter for Curt Trailer Brake Controllers

(457)

$13.44

Hook Probe Circuit Tester

(60)

$13.72

Question:

I purchased and installed the Curt Discovery Trailer Brake Controller - 1 to 4 Axles - Time Delayed Code: C84VV-C51515 using your 7 to 4 way install kit part # ETBC7. It was installed in my 1999 GMC Suburban. I hard wired all the components per the instructions and the video. Heres the problem: When the trailer is not connected every thing works fine on the Suburban. When I connect the trailer, and press the brake I get the OL code. Every thing else works fine signal lights, brake lights running lights etc, but the trailer brakes do not respond. The trailer is new. But to be sure I went to the trailer dealership and tried it on several other new trailers. The result was the same. So its not the trailer. I checked all the wiring and connections especially the blue wire that I made with the install kit and everything is good. Good butt connections, no nicks etc. When I press the brake there is no current on the blue wire coming out of the controller. Could I have a bad controller? Thats the only thing I can think of. Do you have any suggestions? Thanks

asked by: Jim H

Expert Reply:

The issue you're describing likely has to do with the red brake input wire coming from the Curt Discovery Brake Controller # C84VV and corresponding harness # C51515.

You will want to make sure that this red wire is connected to the cold side of the brake light switch behind the Suburban's brake pedal. This is the wire that ONLY gets power when the brake pedal is depressed and no power with any other function. I recommend using a circuit tester like # PTW2993 to verify you have found the correct vehicle wire.

If this connection is correct, then there might indeed be an issue with the brake controller itself. To test this, you can sever that blue brake output wire a few inches back from the controller. Then test the wire for power when using the manual override (not the brake pedal) on the controller. If you still don't get power, then the issue is likely with the controller, and it will need to be replaced.

If you do get power, then the controller is good. You said you traced along the blue wire going back to the 7-Way for any pinched or exposed areas that might be causing a short but also make sure the connection made to the back of the 7-Way is secure.

If you still aren't able to locate and resolve the issue, please let me know and we can continue to troubleshoot.