Troubleshooting Trailer Brakes Locking Up When Applying Brakes in 1993 GMC Topkick

Question:

I have a 1993 GMC Topkick. We recently installed the Journey HD brake controller, and wired it for our 4 horse living quarter horse trailer. Everything appeared to work properly, all the lights coming on at the appropriate time, and we thought the brakes just needed adjusting with a load. However, when we loaded and started down the road, every time we touched the brakes the trailer brakes COMPLETELY lock up. Even with the controller set to 0......

asked by: Darcy

Expert Reply:

I first recommend making sure that your trailer brake controller is properly adjusted. On most controllers, you are able to adjust the settings to control the amount of power that is initially supplied to the brakes on the trailer. I am not too familiar with the Journey HD unit, but your manual should list the specific steps needed to adjust this setting.

If the controller is set up properly, I next recommend checking both the vehicle side connector on your Topkick and the trailer side connector for any debris or corrosion that might be built-up behind the pins. When the trailer brakes completely lock up when touching on the brake pedal in the tow vehicle, it frequently is a result of the stoplight circuit shorting out to the brake output circuit. You can test this theory by seeing if the trailer brakes pulse when activating the blinker in your Topkick. Because the brake output circuit and right turn/stop circuit of the trailer's 7-Way are right next to each other, corrosion can essentially bridge the two pins together over time, which will cause them to short into each other. Cleaning the connector out should resolve this. You will also want to look for any cut or exposed wires going back from the connector.

If this does not resolve the issue, please let me know and I will be happy to look into this further.

expert reply by: Chris R