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Adding Reverse Lights on Boat Trailer to Maintain Reverse Lockout on Coupler


I have done days of research and my brain is now numb. I want to add reverse light on my boat trailer to launch in the dark Towing vehicle has a 4 flat and an out dated 6 pole round wiring Boat trailer has a 5 flat of which one wire blue being for the surge breaks. I currently plug the 5 flat and 4 flat to tow and lose the reverse surge break actuator. 1. Adding reverse light will require me to discontinue using the 4 flat and go to the 6 pole round. 2. Not sure but I believe the 6 pole contains a reverse and a power wire. 3. The 5 flat blue wire on the trailer only goes to the tongue where the surge break actuator is. It does not go to the back of the trailer. I want to retain the current wiring integrity and run appropriate ground, reverse etc from the plug to the the back end of the trailer where I will be placing the lights. as well as can be with out tearing it all out and rewiring. I have looked high and low for a 6 pole to a 5 flat adapter but to no avail. 7 to 4, 7 to 5, 7 to 6,4,5, 6 to 4 but no 6 to 5. That being said I need some confirmation or alternative on changing out the 5 flat to a round 6 pole and add reverse light wiring. Iwhew!!!! Appreciate your advice


Helpful Expert Reply:

Let's work on getting some feeling back into your brain! I will break down the easiest solution for what you are wanting to do into two separate sections; your tow vehicle and the boat trailer.

Starting on your tow vehicle, the easiest route to take is going to be to use a 4-Way to 5-Way adapter like the Tow Ready # 20036. This will plug right into the existing 4-Way to provide a 5-Way flat on the other end to match what you have on the trailer. The additional blue wire coming from the harness is what you will use to splice into the reverse light circuit wire behind the tail light.

Another option if you don't feel like worrying about a separate adapter would be to simply cut off the 4-Way connector and wire in a 5-Way harness like # C58545, again connecting the blue wire to the reverse light wire to activate that function.

There are a couple reasons I shy away from utilizing the 6-Way round on your vehicle. The first is that it's very possible the 6-Way is wired for 12V function at the center pin instead of for reverse lights. There are two common ways to wire up a 6-Way and unless you (or a previous owner) specifically installed that 6-Way to utilize reverse lights on a trailer there's a better chance that it's wired up for 12V power, in which case you would have to do some re-wiring on the vehicle side. Also, even if the 6-Way round was wired for reverse circuit function, as you mentioned in your question there isn't an adapter available to connect it to a 5-Way flat so you would still need to do some extra modifications to make it work.

Moving on the trailer side, what you can do is keep the 5-Way exactly how it is but sever the blue reverse wire between the back of the connector and the reverse lockout on the coupler. On the bare wire coming from the back of the 5-Way add a butt connector like # DW05745-5. This is where you can combine both the reverse wire coming from the lockout circuit and the 16 gauge wire # 16-1-1 that will be run up from the newly added reverse lights at the rear of the trailer. Both will then carry the reverse light circuit coming from the tow vehicle when utilized.

I have attached a link that will take you to our complete selection of reverse lights that you can also look through if you don't have them already.

helpful expert reply by:
Chris R

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