Troubleshooting Trailer Brakes that Lock Up When Trailer Is Connected

Updated 09/26/2016 | Published 09/24/2016

Products Featured in This Question

Curt Discovery NEXT Trailer Brake Controller - Up to 4 Axles - Time Delayed

(61)

$113.95

Curt Custom Wiring Adapter for Trailer Brake Controllers - Dual Plug In

(199)

$36.21

Question:

Installed controller with purchased C51382 wiring. When there is no trailer attached and the brake pedal is pressed the controller lights up with a single decimal, which I understand to be correct. When I hook up a trailer, all the lights work properly I previously had a 4-pin installed so the relay from that is still installed under the passenger side floor panel but there is nothing on the Discovery display. I still get a decimal appearing when I press the brake pedal but the trailers brakes are locked up. When I turn my truck off the brakes are released but they lock up again when I start my truck up.

asked by: John

Expert Reply:

There is a short or a mis-wire on the 7-way you installed. It sounds like the 12 volt accessory circuit is shorting out to the brake output circuit which is causing the brakes of the trailer to lock up anytime the 7-way is connected. This is a fairly common issue as wiring up connectors is a bit confusing. Since the controller never senses a connection it sounds like the problem is the circuits just being wired backwards.

I attached a chart that has what the 7-way pin out should look like.

expert reply by: Jameson C