Do we have a resident electronics/wiring guru here?

  • I want to hook my rear wind screen lights to only come on when I hit the brakes. I know you need to use a relay but I'm uncertain about which wire goes where...because someone said something about the brake light ground is hot ....not sure..I blew out one set of lights...thinking adding one more light in the brake light circuit should not be a big deal...using convention wiring. Red hot, black not.


    I already screwed things up once.....don't want to take it to the dealer again...for something I broke.


    There is a good reason to do this....first at night it's very hard to see anything in my rear view mirror when the lights are on steady with the flame design etched in. Second it would eliminate the colored lights being on and visible all the time to LEO. I'm thinking if it only comes on when you hit the brakes .....it kinda looks and acts like an actual brake light...at least you could try to use that argument.


    I'm using a color combination of red, yellow and orange LEDS to more accurately look like real fire...that's still a work in progress to figure out the number of each color to best simulate fire. Solid red doesn't look like fire...solid yellow doesn't...solid orange is close.

  • Just spit balling here. But, the proper way would be to power the wind screen lights off of their own circuit and only use the brake light as a trigger for your relay. If we have to explain how to do that then you probably shouldn't be messing with your vehicle's electronics. If you've already done damage before you may want to have a professional do the work or hit up a wrench day and have a more skilled person take a crack at it. If you were closer I'd be more than willing to complete the wiring for you.

    When life knocks you down, calmly get back up, smile, and very politely say, "Is that all you've got?

    Edited once, last by WraithSS ().

  • I originally wanted it to be on all the time. I actually had it wired on the bench to be half brightness all the time and when the brake was hit it went to full brightness.... that's fairly easy to do....but that's where I got into trouble I hooked it up on the bike and things went wrong...


    Because of the way the brakes are wired....


    Someone suggested using a relay to light it from the brake light.... I bought heavy duty relays....I just need to figure out which post on the relay hooks to what....


    I have given up on the idea of having it lit all the time... it's really bright and I don't want pulled over for having visible colored lights on that can be seen from the front....that's why I'm going with the brake light idea...


    And I'm not really the kind of guy that's going to park it with the lights on..for show. I'm all about function.


    I could still be able to do the dim/bright thing with a relay. I'll have to think about that some more...if it's only half as bright it's still visable from the front..and it does interfere with back vision.


    I think the flames lighting up with the brakes is a cool idea...it will get the attention of the drivers behind me...that's my intention...

  • If I were going to do it, I would do it this way.


    I would get a relay like this, 547476_0_0


    Then I would tap off the wires coming from my 3rd brake light, one going to terminal 85 and one going to terminal 86 of the relay. Doesn't matter which is which.


    Then I would tap 12 volts off my license plate light, the Dark Green with Pink stripe according to the Service manual (but I would test with my meter) and take that to terminal 30 on my relay. Then I would take the 12 volt (or hot wire) off my rear wind screen and connect that to terminal 87a of the relay. Then I would connect the negative wire of the rear wind screen to ground.


    Below is are some diagrams of a typical automotive relay.


  • Thanks ...Ok, if you use the wire from the license plate light will that make the wind screen light up all the time? Or is that just to power the relay? I'm electronically challenged.


    No worries. I'll try to explain.


    My understanding is that when you press the brake pedal the brake circuitry grounds. So what this should do in theory is make the rear wind screen come on only when you brake.


    This is how it works. Reference the wiring diagram on the right in my post above. The terminals 85 to 86 are your activation circuit if you will. So when 85 to 86 are energized whatever is connected through terminals 30 to 87a will not pass power. Then when you press the brake, if the brake circuitry does actually ground, then 85 to 86 will deenergize and pass power through 30 to 87a, thus lighting the rear wind screen when braking. It would be important to use a 12 volt source that is only on when the sling is on. Otherwise you would light your rear wind screen when turning off the Slingshot as well as when braking.


    Hopefully that makes sense...

  • Good write up. That is how the brake power does work. I wired a trailer harness off the brakes back on TDS. It took 5 relays to make it work with ground providing control of the brake lights.

  • Alright I just watched a video about relays and it got me thinking about the possibility of burning out the brake light switch from fluctuating power as mentioned in an above post.


    Instead of taking power from the brake light....can we somehow tap off the brake light switch after it's energized or is that the same thing? Or is there another place to get the power so as not to involve the switch?

  • Alright I just watched a video about relays and it got me thinking about the possibility of burning out the brake light switch from fluctuating power as mentioned in an above post.


    Instead of taking power from the brake light....can we somehow tap off the brake light switch after it's energized or is that the same thing? Or is there another place to get the power so as not to involve the switch?

    You've been given options for power before. Either use it's own circuit (recommended) or find another source that can handle the load of what you are adding. Do you have the equipment to test that?

    When life knocks you down, calmly get back up, smile, and very politely say, "Is that all you've got?

  • Trust me, I'm not trying to be a bull head...I'm trying to understand the brake circuit ground thing...


    I have two questions about the entire wiring diagram...


    1 where is the brake pedal switch on the diagram (what's it called?) and did they interrupt the ground wire in that switch?


    2 in the middle of the diagram there are splices. Where on the SS are all these splices located.

  • If I have this correct...there are actually two hot wires going into the relay


    The hot wire from the 3rd brake light...when brake pedal is pushed.....connected to 85
    Ground wire to 86



    And the hot wire from the license plate light.... connected to 30


    Wind screen red goes to 87a and windscreen black goes to the frame?

  • You lost me at "I can't see anything in the rear view mirror".


    Pretty sure its not light related ;-)

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  • Why buy one when you can have two at twice the price..... :evil: