Troubleshooting Electric Brakes Locking Up on Trailer

Updated 11/24/2017 | Published 11/23/2017

Question:

I have 2018 big tex dual axle trailer . the front axles are locking up periodically . I have replaced the brake controller in the truck . I disconnected the plug from the truck and of course they didnt lock . I then hooked up to my other truck and everything works great . so i eliminated that scenario that something was wrong with the trailer brakes . so i do know it is something with the other truck wiring/plug ? Keep in mind this is something that has just surfaced it has been fine before . Where do i start and what do i test now ? your knowledge would be much appreciated as this is driving me nuts

asked by: Bob B

Expert Reply:

Since you seemed to have narrowed the possible cause down to the vehicle side of your setup, I recommend starting with the 7-Way connector at the rear of your tow vehicle. Check for any corrosion or debris build-up inside the connector that might be causing a short and clean as needed.

If the connector looks fine, use a multimeter like # PT89ZR to test for voltage at the brake circuit on the connector when you have the brakes applies using a low setting. With this setting, you should see a number well under 12 volts, as 12 volts is the maximum output of a brake controller. If you are seeing 12 volts, then there is an issue somewhere along the wiring going up to the controller or possibly with the brake controller itself.

First check for any obvious causes of a short, such as damaged or frayed wiring, simply fixing as needed. If everything looks okay, move to the trailer brake controller inside the vehicle and sever the brake output wire, which should be blue, from the back of the controller. Repeat the same steps performed above with a multimeter to see if you get the same 12 volts with the controller set at a low setting. If this is the case, then the issue is with the brake controller itself and it will need to be replaced.

If you see a lower voltage when testing there, then there is an issue somewhere on the wiring between the trailer connector and brake controller. Inspect the wiring again and fix any issues as needed.

If you are still unable to find or resolve the issue, please let me know and we can continue to troubleshoot.

expert reply by: Chris R