Troubleshooting Tekonsha Prodigy P3 Brake Controller Not Working Correctly with Headlights On

Question:

I have 2002 Dodge Ram 2500 Diesel with a Tekonsha P3 Brake Controller. When the headlights are off the controller works perfectly. But when I put the headlights on the brake controller is intermittent. When I apply the brakes and release the brake pedal the trailer disconnect comes on and recycles and than resets as connected. I have replaced the headlight switch, and the trailer relay, new blue and white wire. There was improvement with a new trailer relay. The trailer disconnect was for a shorter time.

asked by: Larry W

Expert Reply:

It sounds like there might be a short somewhere on the trailer wiring, specifically between the running light and brake output circuit. I recommend first just inspecting the 7-Way connector on both your Ram and the trailer for any corrosion or debris around the pins that might be causing this short, cleaning out as needed. Also check the wiring at the back of each connector to see if you can find any pinched or exposed wires that need to be replaced.

The other possibility is that the red wire from the Prodigy P3 # 90195 is not connected to the correct brake switch wire on the truck if it was hardwired. The red wire should go to the cold side of the brake light switch, which is the wire that ONLY gets power when the brake pedal is depressed and no power with any other function. Also just make sure that this connection is sound and there aren't any pinched sections of wire.

If this does not resolve the issue please let me know and we can continue to troubleshoot.

expert reply by: Chris R