Troubleshooting Trailer Brakes that Lock Up When Trailer Connector is Connected

Question:

When i hookup the 7 pin connectors to one another the electric trailer brakes come on. Releases on unhooking. Could it be wired differently on the ford or trailer? I was told ford wires them 2 different ways ... if I use my 7 pin to 4 pin adaptor lights and brake lites work fine but no brakes.

asked by: Jimi

Expert Reply:

It sounds like the 12 volt accessory circuit has either been ran to the brake output circuit or it is shorting out to it. Most likely the problem is on the trailer wiring side of the equation as it looks like your truck is brand new.

If you check out the diagram I attached you will see how a 7-way connector is typically wired for you to compare to the 7-way on your trailer.

To check for shorts you would need to go over the wiring of the connectors looking for any bare wire that might be touching each other.

expert reply by: Jameson C