Troubleshooting Primus IQ Brake Controller that Has Brake Output Reading all the Time

Question:

I purchased a truck that has the Primus controller already installed... Recently we purchased a 5th wheel camper... On our way home from out last trip I felt the camper jerking around and noticed the number changing rabidly on the controller... I disconnected the controller and drove home on truck brakes... I did notice I had a bad ground and that has since been fixed... Everything works as the instructions state until I turn the truck on and then I automatically get a reading of around 1 on the controller without be even touching the brakes... Also when I depress the brake pedal nothing changes on the display...

asked by: Jeff R

Expert Reply:

There's most likely a short between your 12 volt (black) power wire for the brake controller and the stoplight circuit (red) wire. Check the red wire of the controller and fix any obvious shorts as needed. Since there's power on the red wire of the brake controller it thinks the brakes are applied so it's actively trying to sense vehicle braking activity and then applying the trailer brakes in relation to what it senses.

expert reply by: Jameson C