Troubleshooting Trailer Brakes that Lock Up When Vehicle Brakes are Tapped
Published 05/03/2018
Question:
My truck has a new 7 way plug installed and when connected to our trailer all the lights and turn signals work, but when I start to pull the camper and I tap the brake pedal the trailer brakes fully engage. Where should I begin in order to diagnose the issue. Thank you
asked by: Paul W
Expert Reply:
One of the stop/turn signals on your trailer wiring is shorting out to the brake output which is putting full 12 volts on the brakes when the brake lights come on. To further figure out which blinker is the problem try putting on either blinker. You should see that one of the blinkers causes the brakes to lock up with each flash. That's the side that's shorting to the brake output.
From there you need to check all the connectors and wiring for a short between those two circuits and fix as necessary.
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