Troubleshooting Trailer Brakes Locking Up When Running Lights of Vehicle are Activated

Question:

Re: Jayco Model 19H Jay Feather EXP travel trailer: Problem - 12 volts to trailer brakes when running lights activated. A little alarming when auto on headlights come on when driving down the road and trailer brakes lock up. Fortunately I was in town and only going about 20 mph so no appaent flat spotting on tires. Tow vehicle is a 2016 Chev Silverado. GM dealership checked vehicle wiring and everthing OK. Suspect short in trailer wiring. An orderly approach to finding the problem would be appreciated. Thanks

asked by: Martin B

Helpful Expert Reply:

What you have is a short between the running light and brake output circuit on your trailer wiring. This is going to be caused by exposed wire on both circuits touching each other. What you'll have to do is start at the trailer connector and work your way back on both circuits fixing any obvious shorts. Also inspect the 7-way for any bent pins or corrosion and fix as needed.

expert reply by: Jameson C