Troubleshooting Trailer Brakes Lock Up When Connected to Tow Vehicle

Question:

Greetings I have a elderly neighbor that has a pacesetter trailer. He had some stuck working on it and now when he connects the trailer to his pickup with the battery on the trailer connected his brakes lock up. If he unplug the trailer plug it works fine. Before he brings it over to me to take a look at it do you have some ideas on where I should start looking? It has a round 7 pin plug with 5 wires coming out of it. Thanks so much.

asked by: Randy

Expert Reply:

I'm not sure what work was done on it, but I would be checking the connector. Based on what you described there is constant 12V power on the brakes. Assuming it is the trailer side, it is possible the trailer has corrosion on the connector. It could also be a short in the wiring somewhere, or based on the fact the 7-way has 5 wires it could be wired incorrectly.

Try checking the 12V power wire on the trailer with it hooked up to the truck using a circuit tester like # PTW2993. If there is no power on this wire I'm betting the brake output wire is where the 12V power wire should be. If everything checks out on the trailer I would be checking the connection on the truck. Assuming you have a vehicle with a 7-way you could rule that out pretty quick by plugging the trailer into your vehicle to see if it does the same thing.

I have attached a help article on 7-way wiring below for your reference.

expert reply by: Robin H