Trailer Brakes Lock as Soon as Trailer is Plugged Into Tow Vehicle

Question:

When I hook up the electric to my travel trailer my brakes lock up tight. It will happen with any vehicle used. I have rewired 2 trucks and the trailer from the tongue to the junction box. I have had the brakes checked and they seem to be ok too. Im wondering if the problem is the magnets. Do the magnets lockinch when receiving electricity if they are worn? Or, could it be a short in the wire at the drum? I can move the trailer if its not hooked to the electric wiring, but it wont budge as soon as I plug it in. The bad part is my trailer is like new, 2006 with maybe 2000 miles on it. I have asked many dealers and garages but no one seems to know how to deal with or test the magnets. After some research, I understand the concept of the magnets, but have not seen or heard anything about the wheels getting locked. Of course Im a woman trying to fix it on my own... Dont roll your eyes, just HELP! Thanks!

asked by: Rhondag

Expert Reply:

I have a sneaking suspicion that your travel trailer might have a 6-way connector on it, but your truck has a 7-way, and you're using an adapter like part # 47549. Am I on the right track?

There are two accepted ways of wiring a 6-way trailer connector. One uses the center pin as the brake output circuit, the other used the center pin as the 12-volt power feed to the trailer. If the connector on your trailer is wired one way, and your adapter is wired the other, it would cause your trailer brakes to lock immediately when the trailer is plugged in.

An adapter like # HM47570 allows you to easily swap those circuits without needing to rewire anything. I've linked you to an FAQ article that shows how the adapter is used.

expert reply by: Mike L