Troubleshooting Brake Controller that Shows Voltage Readout without Brake Applied

Question:

I have a 2008 Chevy Silverado with the Tekonsha Primus IQ TK 90160 brake controller installed. Seemed to work fine at first but now shows brake power to the trailer while driving. The readout will fluctuate up and down while driving up to 3.2 and back to 0.0. Sometimes it will stay on 0.0 if I hit the brake pedal, but not all the time. Ive double checked my wiring and inspected wires for breaks and frays and everything looks good! Please help! Thanks,

asked by: Dan L

Expert Reply:

Typically the problem you described comes from the red wire of the controller either shorting out or the controller not mounted properly. Since you said you checked the wiring what you can do is test the controller using our troubleshooting steps to determine where the problem is and if you need to replace the controller.

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 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.

For a brake controller replacement I would recommend the Prodigy P2 Brake Controller part # 90885. This is our best selling brake controller because of how well it works and how easy it is to setup. This is a proportional brake controller that senses the amount of braking the tow vehicle is applying and applies a proportionate amount to the trailer brakes.