Why Would Trailer Brakes Lock Up When Running Lights are On

Updated 07/11/2018 | Published 07/10/2018

Question:

I was towing a trailer last week about 5:30 in the morning and after several miles smelled hot brakes. I pulled over and the brakes were smoking on the trailer. After checking everything, I discovered the brakes are staying on when the trucks lights are on, then the brakes dont work at all with no lights. I was able to get it to an RV center where testing showed the issue is in my trucks wiring. Its not the brake controller itself, because it works fine in my dads 99 K2500. Vehicle in question is a 2005 GMC Sierra 1500 CCSB 2wd with 5.3/4L60E. Also, what would be some good, simple upgrades to make this truck tow better?

asked by: Matt K

Expert Reply:

There's a short on your trailer wiring between the running light circuit and the brake output circuit that runs to the trailer brakes. Look for exposed wire or corrosion on the wiring and connectors and you'll find the short.

Rear suspenion enhancement like the Timbren kit part # TGMRTT15S would be a great way to help with towing. It will give more more support to the rear suspension to allow it to tow level.

expert reply by: Jameson C