Constant Power of Blue Brake Controller Wire and Intermittent Power on White Wire

Question:

I have a 1997 dodge ram with a voyager xp brake controller. I get a constant hot signal on the electronic brake at the back of the truck and the light get brighter as the c[brake is applied. I also found a lose wire that lights when the brake is applied and goes out why not applied. it splices into a whit wire in the front of the truck. is this a ground wire and if so why does it show a load when the brake is applied? Also why do I ave a constant load on the blue brake feed? it the control bad? Help please as this is getting very confusing and the videos make it seam very simple.

asked by: Dan

Expert Reply:

It does sound like your brake controller is bad but there is some testing that you can do to determine if that is the case. First we should go over the functions of the wires.

The white wire is the ground. If there is power on this wire, then that would indicate a short to ground. The blue wire is output to the trailer brakes. It should only have power when you apply the manual override or step on the brake pedal with the vehicle moving. Red is input from the brake switch that should only have power when you step on the brake pedal. And black is 12-volt power to power the controller.

In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2993 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override. If it shows power at idle, then there is something wrong with the controller and it will need to be replaced.

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 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.

I have also included a couple of links to some help articles for you.

expert reply by: Michael H