Should the Brake Output Circuit have 12 Volts without Brake Pedal Pressed

Updated 07/22/2014 | Published 07/21/2014

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Question:

Should there be 12 volts at the truck receptacle, 7-pin for trailer plug between the blue and common ground when the brake pedal is not depressed?

asked by: Steven M

Expert Reply:

No, the brake output circuit of the 7-way on your truck should not be showing 12-volts when the brakes aren't applied. This circuit should have no voltage unless the brake controller is activating either with the manual override lever or by pressing the brake pedal. Either the controller is broke and is sending voltage when it shouldn't or the 12 volt circuit of the 7-way is shorted out to the brake output circuit.

Testing the brake controller is fairly easy. Sever the blue brake output wire and then apply the manual slide. Using a circuit tester like part # PTW2993, you should get output to the trailer brakes. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide are not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire. On the red wire you will only want power when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded then there is possibly a problem inside the brake controller.

I am including a link to a video that will show you how to test the wiring on a brake controller. I also attached an FAQ on troubleshooting brake controllers.

expert reply by: Jameson C