Turn Signal and Tail Light Circuits Work But Brake Light Circuit Not Working on RV Trailer Connector

Question:

I have a class A motorhome. We are planning to Dingy tow our Durango. As you can see from the picture, the Class A had a 6 wire plug. I have cut off the plug and attached a 4 wire plug white, green , yellow, and brown. I left the red and black not connected. It all seems to work except when I push on the brakes. I I have a flat 4 test plug that I attached to the Class A. The test plug shows the same issue. The test plug did not light up when pushing the brake. This tells me the problem is from the Class A. Why would the turn signals work, but not he stop light?

asked by: Scott S

Expert Reply:

The 6-Way square plug on the RV most likely indicates that it uses separate circuits for the brake lights and turn signals. You will need a converter to combine the brake and turn signal circuits and then wire the output wires from the converter to the 4-Way flat.

You could just use # 119178. On it the white wire is ground, red is input for brake lights only (probably that red or black wire you did not connect), green is right turn signal, yellow is left turn signal, and brown is running lights.

expert reply by: Michael H