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Vehicle 4/5 pin to trailer 7 pin

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  • Vehicle 4/5 pin to trailer 7 pin

    Has anyone found an easy solution to an older tow vehicle with a 4/5 pin to be able to convert to 7 pin on trailer?

    I was hoping to not have to rewire. I only trailer twice a year < 1 mile.

    My current set up has a 4 pin that I upgraded to a 5pin on the vehicle side. I have a 2021 XT21 being delivered shortly and hadn't thought about this detail until now. I believe the new trailers are 7 pin. I came off a 2008 trailer with a 5 pin.

    Are people using something like this 4 pin to 7 pin converter?

    https://www.etrailer.com/Wiring/Curt/C57674.html

    I've already isolated/tapped into my reverse wire (vehicle side) so I can add that in (yellow wire on curt new piece)
    I will mount the white wire (curt new piece) to the frame as the ground wire

    To make my trailer and brakes work...

    1) Do I need to run the charge line cable (black wire 12v power wire)?
    2) Do I need to run a connection to the battery for the blue wire to control the brakes?

    thank you for your input.

    Happy to post pics once I finalize my plan

  • #2
    I believe that the blue wire on the 7 pin is the output of the trailer brake controller. On my cargo trailer with electric brakes, if I wired the blue wire to the battery, the brakes would be activated all the time! So my quick answer is you do not want to do that. To make the electric brake activation work correctly, you need a trailer brake controller. Curt also makes several add on ones. One works using your phone and doesn't hard wire to your car, if you want to go that route.

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    • #3
      I swapped a 4 pin to a 7 pin - Of course, the other stuff (brake controller) did not work/not connected. For the reverse lock out, tapped into the rear brake light.

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      • #4
        they have a round converter that goes from 7 pin to 5 pin...

        you can buy this one or do it yourself... it's pretty easy...

        https://www.towuniverse.com/7-way-bl...n&currency=USD

        most autoparts/fleetfarm type stores carry them...

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        • #5
          Boat trailers do not need the charge line, that is for RVs and powered utility trailers like a hydraulic dump trailer. The brake line is for a brake controller to control electric brakes, which most boat trailers do not have.

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          • #6
            You can also get a small length of wire and the two plug you need and make you own adapter pretty cheaper.

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            • #7
              I used the same thing you have and added a lighter plug to supply 12V power and ground. Our super cool minivan has a 12V lighter plug near the back I use, which was easy.

              I didn’t do anything for brake lockout as my trailer has surge brakes.

              Works fine, although I tow about the same as you except for a 15 mile tow I had to do vs barrowing a truck.

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              • #8
                Originally posted by MIskiboat View Post
                I used the same thing you have and added a lighter plug to supply 12V power and ground. Our super cool minivan has a 12V lighter plug near the back I use, which was easy.

                I didn’t do anything for brake lockout as my trailer has surge brakes.

                Works fine, although I tow about the same as you except for a 15 mile tow I had to do vs barrowing a truck.
                Electric brake lockout (reverse wire) or a manual lockout on the tongue are needed for surge disc brake trailers. Not quite as necessary for drum brakes.

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                • #9
                  Originally posted by Tsumi View Post
                  Boat trailers do not need the charge line, that is for RVs and powered utility trailers like a hydraulic dump trailer. The brake line is for a brake controller to control electric brakes, which most boat trailers do not have.
                  This has historically been true, but not any longer. Most boat companies are offering electric trailer brakes as an option now.
                  -----------------------------------
                  Mastercraft ProStar 2019 5.7L - Current
                  Mastercraft X25 2014 6.2L - Current
                  Nautique 200 OB 2012 5.7L - Current

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                  • #10
                    Originally posted by jpwhit View Post
                    This has historically been true, but not any longer. Most boat companies are offering electric trailer brakes as an option now.
                    That's true, and it's a long overdue change. It should be standard on anything over 6k lbs. If OP got the electric brake option, he will need a brake controller as well.

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                    • #11
                      Ok so new boat is here! Still buzzing inside so I haven’t calmed down yet.

                      I took a look a the 7 pin from the trailer and it only uses five wires. No charging and no electric brake. I spent so much time on the boat selection that I didn’t think about the trailer electric brake option. This works out fine for me.

                      I’ve learned a lot about trailers in the last 24 hours and appreciate the dealers explanations.

                      The manual lock out is a great option for those who want to do the least wiring change from 4 to 7.

                      Adding the reserve wiring brings you to 5 wires but you need to tap into your reverse lights.

                      As others have stated, Adding the electric brake option requires adding wiring in the brake wire.

                      I hope to install this weekend and will post pictures.

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