Troubleshooting a Fifth Wheel Trailer that Activates Truck Brake Lights When Connected

Question:

I recently purchased a 5th wheel trailer, when I plugged the harness into the outlet on my truck my brake lights on my truck came on but no trailer lights.

asked by: Brian L

Expert Reply:

Sounds like you are going to need to clean up the trailer wiring connectors on either the truck or the trailer. First thing you will want to do is use a circuit tester like part # PTW2993 to test all of the pins on the connector you have on your truck and make sure they match what you see in the diagram I attached. If that checks out then the problem has to be on the trailer's connector.

You would want to first check the connector for corrosion and fix as needed but then you would also need to be sure that it is also wired the same as the truck 7-way. You can take a jumper wire from the vehicle battery to put voltage on each pin to see the function of them all.

expert reply by: Jameson C