Connecting 4 Flat to 7 Round for Boat Trailer with Surge Brakes

Updated 09/03/2020 | Published 09/02/2020

Question:

I have a boat trailer with surge brake. Im installing a 7 round adapter using my existing 4 flat plug. I plug the 4 flat into the existing 4 flat to get all the lights. I have 1 white which I know is the ground. I have 3 wires left with connectors on the end. A blue, yellow and black. Which of these do I need to use? And where do I splice them in?

asked by: Paul R

Expert Reply:

It looks like you're using an adapter like the # ETBC7. I attached a picture to show the functions of each wire as well as a video review so you can see it in action.

Attach the yellow wire to your reverse light circuit on your towing vehicle. The yellow wire is the auxiliary wire for your reverse lights or reverse lockout on your boat trailer. The correct wire is only hot when your vehicle is in reverse.

You don't need the blue and the black wires for your boat trailer. Just tape them up and tuck them away. Ground the white wire to your truck frame.

expert reply by: Evangeline M