Troubleshooting Gooseneck Trailer Brake Lights that Stay on all the Time

Question:

I have a 2007 dodge 3500 flat deck pulling a 35 foot goose neck trailer brake lights stay on all the time during recent cold snap

asked by: Garry P

Expert Reply:

It sounds like the 12 volt accessory circuit of the trailer connector on either the truck or trailer side has shorted out to your brake light or running light circuit and it's activating the circuit all the time.

Typically it's corrosion on the front or the back of trailer connectors that causes this problem so that is where I would start first.

To isolate the problem to either the tow vehicle or the trailer you can use a circuit tester like part # PTW2993 to test for voltage on the trailer's connector in all of the correct places. See the FAQ article I attached that has all of the different trailer connectors available and their wiring diagrams.

Next, you will need to inspect the wiring of the trailer and the vehicle's trailer wiring looking for any cut or exposed wire that would cause a short and fix as necessary.

I attached a couple FAQ articles to the right that you should find helpful as well.

expert reply by: Jameson C