Troubleshooting Trailer Brakes that Lock Up when Trailer Connector is Connected
Question:
I have a 2010 Chevy 2500 truck. When I connect to a trailer the brakes lock just buy plugging in the harness. If I unplug it the brakes release. I check for voltage on the plug on the back of the truck and it shows 3.6volts without pressing the brakes. Other trucks hook on the same trailer with no problems. I understand that 3.6 volt should not be a problem. Is this right?
asked by: Bobby
Expert Reply:
If you are seeing 3.6 volts on the brake output circuit of the 7-way you have installed on your tow vehicle that would explain why your brakes are activating when the connectors are connected.
If the brake pedal is released on your 2010 Chevy 2500 Silverado and the manual override of your brake controller isn't engaged you shouldn't see any voltage on that circuit.
Testing the brake controller is fairly easy. Sever the blue brake output wire near the brake controller leaving enough room to reconnect it and then apply the manual slide. Using a circuit tester like the part # PTW2993, you should get output to the controller side of the wire you severed. 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.
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