Troubleshooting Trailer Brakes That are Locked up on a Gooseneck Trailer

Question:

I have a 2004 Toyota tundra, I have been kicking it in the ass pulling 3 beam, double axel gooseneck trainer since the day I got the truck. Never had really had the breaking that I wanted on the trailer, however, the trailer did have breaks, but, weak. I started having a problem with no breaks at all. Changed the battery on the trailer, and the trailer breaks started locking up. I had an old Tekonsha system and questioned its functional status even though the out-put was correct on the trailer plug on the bumper of the truck. I purchased the new Tekonsha Primus IQ Trailer Controller with the harness to hook directly into my Tundra. Got back from a trip today, hooked it up, all electrical was working fine on the plug at the bumper, and my trailer continues to lock up the breaks. I assured all wires at the plugs are tight. When I troubled shot at the trailer brakes, the trailer breaks had power at the drums even when the brakes on the truck and the controller were not applied. Again I tested the female plug on the truck and it is working fine, with only the hot wire being hot until power applied. Thus, my question is Why is the power noted at my trailer drums when no breaks are applied, why are my trailer breaks locking up???

asked by: Howard N

Expert Reply:

Sounds like your breakaway system has the pin pulled or the 12 volt accessory circuit of your trailer's wiring is shorting out to the brake output circuit.

You can test this pretty easily by testing the voltage at the brakes like you already did but without the trailer wiring connected. If the voltage is still there then it's somehow related to your breakaway system. Most likely the pin is partially pulled out or something went wrong when you installed the new battery.

If the voltage disappears on the brake circuit with the trailer disconnected you know that the problem is that the 12 volt accessory circuit is shorting out to the brake output circuit.

Another possibility is that you have a 6-way and the brake output and 12 volt circuit have been swapped as there are two typical methods for wiring a 6-way and the difference between the two is that the brake output and 12 volt circuit are swapped.

Check out the FAQ articles I attached for more info.

expert reply by: Jameson C