Power Always On Blue Wire on Curt Brake Controller on a 2005 Chevy Silverado

Updated 07/07/2014 | Published 07/04/2014

Question:

I recently purchased Controller C74VV for our 2005 Silverado. Installed and connected easily with connector C51352. Tested the blue Brake outlet at the blades in the connector at the back of the truck. It always has power, about 12.65 volts, no matter whether the brakes are on or off. There is power all the time, whether the ignition is on or off. The only time I could eliminate that terminal from being always on was to unplug the controller from the box. Help! Is this a defective product? Or am I missing something? Thanks.

asked by: Robert P

Expert Reply:

Brake controllers do send back a minimum amount of voltage to check for a connected trailer but it should not be enough to activate the brakes.

There are some tests you can perform to determine if the problem is with the controller. First disconnect the trailer from the truck. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use your tester to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override or brake pedal. If it shows power at idle then there is something wrong with the controller and it will need to be replaced. Unless there is something drawing power in the trailer connector. See below.

If it tests fine then reconnect the blue wire. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.

You can test the brake output pin (5 oclock position looking at vehicle side 7-Way) and it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to track down.

If the truck side checks out fine then it could be the wiring to the brake magnets or the magnets themselves. Inspect the power wires to the magnets and look for pinched, frayed, or damaged wires and fix as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces.

You can visually inspect the magnets and if you can see the copper windings coming through the magnets will need to be replaced. To further test the magnets you can follow the help article I have linked. I have also included some help articles on testing and troubleshooting brake controllers for you.

expert reply by: Michael H