trailer brakes on a 2007 silverado 1500 classic
Hello, I am having problems with the brakes on my trailer with my truck. I can apply power straight to the brake wires and they lock, but when I plug it into my truck, they keep spinning. I measured the plug and get about 4volts with the brake controller turned all the way up. My question is, what should the output of the plug be, or what could be causing my problem, thank you.