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Thread: Modulite Trailer Isolation Relay

  1. #1
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    Aug 2006
    Oberlin, OH
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    Default Modulite Trailer Isolation Relay

    Modulite Installation

    Note: The Modulite and similar units are designed for isolating and converting your trailer wiring from the bikes lighting circuit. These units are designed to go from a bikes lighting system which uses separate turn signals to a conventional trailer lighting setup that combines the turn signals with the brake/tail lights. It will NOT work if your trailer uses conventional motorcycle type lighting with separate turn signals. If your trailer uses motorcycle type lighting, you will need to purchase an "isolation" unit. There are several on the market. Bushtec sells their own unit and the Electrical Connection also sells one. Here is a link to the unit at the Electrical Connection.

    This installation is for the Modulite trailer wiring kit.
    The specific one that I used is model 18146. There is more information on this unit HERE.

    There are other models and brands that will also work but this just happens to be the one that I used.

    There are a number of places that this unit could be mounted and other ways that the wiring can be routed to the plug at the rear of your bike. This way worked well for me. This installation is on the Yamaha RSV but these units will also work great on the First Gen Venture or the RSTD.
    I mounted the unit under the seat. This particular model is slender and will slide down beside the battery. Here is a picture of the unit.

    Wiring is fairly simple. Anybody can do this job if you simply follow the instructions and take your time.
    There are 6 wires coming out of the unit from the side that says "To Car"...or in our case..."To Bike".
    There is a black wire that is labeled need to run that wire through an inline fuse and then directly to the positive battery terminal. There is also a "ground" or "negative" wire that will connect to the negative terminal of the battery.
    There are 4 wires that connect to the wiring harness of your bike. An easy place to splice these into the bikes harness is at the natural color connector just behind the battery.

    You can see that I used snap type wire splices for this but I plan to redo these over the winter and use soldered connections. I am just not a big fan of these snap splices. They will work though if you don't wish to do the soldering.
    The connections are as follows.
    There is a green wire marked "right signal" out of the Modulite. Splice into green wire at bike's connector.
    Yellow wire marked "left signal" out of the Modulite. Splice into brown wire at bike's connector.
    Red wire marked "Stop" out of Modulite. Splice into yellow wire at bike's connector.
    Brown wired marked "Tail Lights" out of Modulite. Splice into Blue wire at bike's connector.
    That's it for the wiring. Now just tape up the splices you made.

    These next two pictures show how I slid the unit into the space beside the battery. The first shows it about half way in and in the second picture, it is slid all the way down. I used a tie wrap to secure it there but it wouldn't go anywhere even without one.

    All that remains now is to run the wires coming out of the "To Trailer" side of the Modulite to the hitch of your bike.
    I ran mine across the top of the fender first and under the trunk.

    I then came out from under the trunk and through rubber grommet behind the license plate so that I could route the wires on the inside of the rear fender. As you can see...I also used some wiring loom to cover them at this point.

    Finally, I brought them from inside the fender about the hitch and to the connector. As you can see, I again used some wire loom and also replaced the flat connector with the round type. That is simply a matter of choice.

    That is all there is to it. Pretty simple and works great.

  2. Thanks gggGary gave thanks for this post
  3. #2
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    Oct 2006
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    I have a question on this solenoid thing and what I'm planning on doing (this for each side).
    1) put the oem turn signal across the solenoid side pins 85 and ground to pin 86
    2) put the oem parking lights power lead to pin 30
    3) from pin 87A to the parking light
    4) from pin 87 to the turn light
    Now the way I figure it when not using the turn signal the parking lights in the rear are on. When I activate the turn signal the parking light on that side goes out but the turn lights light up. You should be able to do the because the parking light has it's own connector and the main oem can be split between the two sides.
    I am also putting the solenoids behind the the license plate and running all but the oem wiring into one of those behind the license plate document safes with a terminal strip. This way I can easily connect my HD tail lights, my extra led parking / break lights and the trailer connections. If I am wrong about using the parking lead to power the turn lights let me know.
    Last edited by PGunn; 12-10-2006 at 06:26 AM. Reason: Clear up step 1

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