How to Wire a 4 Pole to 7 Pole Adapter

Expert Reply:

We need to figure out why the trailer lights are not working. Use a circuit tester on your 4-way flat that you plugged into the back of the 4 to 7 pole adapter and test each function to make sure they are working correctly. If your 4-way is working properly, then you can plug it back in and test the corresponding poles inside the 7-way connector to be sure the adapter is working properly. If you need a circuit tester, we have part number 3808.

Next, you would have to plug in the trailer and make sure it is grounded. Also, check the brake, turn and tail lights on the trailer. If the vehicle side is functioning correctly, the trailer side should work or you have a problem there. The black, blue and yellow wires are not related to the taillights and are for other functions. The black wire is for 12 volt power from the battery. The blue wire is for trailer brakes from the brake controller, if you have one. The yellow wire (orange) is for auxiliary power. These wires do not need to be hooked up for the taillights to work. Look at our wiring page (see link below) and it will help you through the process.

expert reply by: Bob G