Troubleshooting Trailer Connector When Trailer Brakes Lock Up When Connected To Vehicle

Updated 11/09/2015 | Published 11/07/2015

Question:

When I plug the trailer into the new 7-way the brakes lock up. When I unplug, they release. Sounds like the same problem stated here. https://www.etrailer.com/question-134409.html Moving 15 hours away on Tuesday. Need help!!

asked by: Brian A

Expert Reply:

To test the connector on your 7-way you would need a circuit tester like part # PTW2993. Test the pins on the vehicle side to determine what the pin functions are. You would need to determine which pins show power when the brakes are pressed on the vehicle. They would be your left brake, right brake, and the brake controller pin. If you have a proportional brake controller there will be very little power on the brake output pin. You would need to test the pin by using the manual override on the brake controller. You can check out the attached diagram to see which pin you should test for current on the 7-way connector.

Then move to the trailer side and use a 12V power source and test those pins as well. You will probably find that the trailer side brake wire is matched with the 12V circuit wire on the vehicle 7-way. You can take the wires loose and connect them to the appropriate pins. I have placed red arrows on the attached photo that shows where the pins are located on the 7-way

You said this was a new installation so the wiring issue may be exactly what my colleague said, and I agree that testing the wiring on the 7-way can help isolate the problem. You can also check the wiring and look for loose grounds, damaged wiring, or even dirty connectors. If this is a new installation, you may want to make sure it is wired properly.

expert reply by: Jeffrey L