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  • Third brake light 7-Way Interface plug-in T Harness - 300100

    • $ 119.99

    Fits most trucks with 7 way trailer plugs  #300100

    Will not fit 2020+ Chevy with the Smart Tow and Advanced trailering system

    Except 2015 -2022 Ford F150, 2016-2022 F-250 and 2016-2022 Toyota Trucks (Tacoma and Tundra)

    Save time and hassle with the 7-Way Interface Harness. Installation takes as little as 7 minutes and gives you the ability to maintain your 7-way connector functionality and OE vehicle wiring. The 7-Way connects quickly and easily, with no need for cutting or splicing of wires.

    Frequently Asked Questions

    Q: What is the difference between the 300200 & 300100?

    A: 300200 is for the newer Fords and Toyotas that require external power source due to the smart towing system.It includes extra wire to run to the battery which is why there is more cost to it. The 300100 fits pretty much everything else

Q: It is for a truck cap with LED center stop light?
    A: Yes.


    Q: Does the Wiring harness provide full-time hot wire power to the dome light on a topper?
    A: Yes.


    Q: Does this install in behind the bumper so that it's concealed and the external bumper mounted plug still operates? Or does this connect to the external bumper plug itself and T from there?

    A: Yes, they both install behind the bumper so that you can still use the external plug for your trailer and not affect usability
    Q: I understand how the seven way connects into the wiring behind the bumper, but my brake light on the camper has only two wires. How will those connect to the four way plug?
    A: There are 2 different style connectors in the package a 6 pin for the Leer fuse box and a 4 pin for the rest of the brands. You will insert the wires into whichever connector you need to match your top 


    Q: Will the 7 way harness Leer part 300200 work with a ford F150 lightning?
    A: Yes, it does if it is newer than 2015

    Q: Do you have wiring to hook up the topper power lock to factory tailgate power lock?

    A: no, all these harnesses do is brake and dome light - 12volt auxiliary
    Q: The issue im having is the brake lights work but there isn't power to the dome light in the cap. I checked all fuses and they're in place and not blown?
    A: The 300100 pulls power from the 7 way plug. The power is not always hooked up from factory. You may have to attach the power lead or add a fuse at the fuse box which is pretty common. Look for "Trailer tow power"

    Customer Reviews

    Based on 35 reviews
    Linda Rodrigues

    Easy to install and works well.

    Cliff Porterfield

    Perfect and easy

    LEER 7-way harness did the job, but...

    The harness adapter works, but was not long enough to reach the power distribution box inside the Leer 180 cap. I had to also use the included wiring in the plastic bag attached to the cap. Took considerable amount of time combining the 2 harnesses using heat shrink butt connectors and the correct size split loom, and routing the harness up behind the left side tail lamp assy. Its done now and working is what counts. In this case def not plug n play.

    Jeff C
    2015 Silverado

    I recently installed a cap and needed power for third brake light and lights within the bed of the truck. This Harness was super easy to install and allowed constant 12 volts for the lighting to be operated by a switch. Highly recommend!!

    Charles Testut

    Works great

    3rd 7-way brake light cf-type-wiring-harness cf-vendor-leer harness leer third