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Wiring circuit advice - please assist

Discussion in 'Gen 2 Prius Accessories & Modifications' started by Justdidit, Mar 16, 2016.

  1. Justdidit

    Justdidit LVNPZEV

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    I'm looking to wire in a AUX light to my reverse lights. As an option, I want to be able to turn the AUX light on without putting the car into reverse as well. This is what I have setup currently and it allows the AUX light to turn on when in reverse with no issues but I can't get the switch to activate the light separately from putting the car into reverse. Every time I flip the switch, it blows the fuse near the 12v input source and never fires up the AUX light. I was wondering if I have the wrong relays or even the wrong switch.

    Please advise. Thank you!

    102438_AUX_Reverse_Diagram.jpg
     
    #1 Justdidit, Mar 16, 2016
  2. jdenenberg

    jdenenberg EE Professor

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    It sounds to me that you reversed the roles of the switch terminals. Does the LED light up when the switch is off? The LED (and its resistor) is wired between the common terminal and the terminal that should be grounded. The switch contacts connect the third terminal to the common terminal (12v goes to the common terminal. Use an ohm meter (or continuity tester to check out the two terminals connected to the switch contacts.

    JeffD
     
    #2 jdenenberg, Mar 16, 2016
  3. Justdidit

    Justdidit LVNPZEV

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    To be honest the wiring diagram on the switch packaging was a bit confusing. When i get home, i'll take a picture of it to see if possible i do have it wrong. No, the led does not light up - at all. I do have an ohm meter but honestly do not have a clue how to use it.
     
    #3 Justdidit, Mar 16, 2016
  4. jdenenberg

    jdenenberg EE Professor

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    Post the switch wiring diagram.

    JeffD
     
    #4 jdenenberg, Mar 16, 2016
  5. Justdidit

    Justdidit LVNPZEV

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    [​IMG]
     
    #5 Justdidit, Mar 16, 2016
  6. jdenenberg

    jdenenberg EE Professor

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    That is the wrong switch as it is for a 120VAC system. You need one that is set up for 12v with and LED, not a neon light.

    JeffD
     
    #6 jdenenberg, Mar 16, 2016
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  7. xliderider

    xliderider Senior Member

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    To be blowing the fuse at the 12v input source, you have to be creating a dead short, so your switch terminals are wrong. Basically, you are switching the 12v + directly to ground and not into your relay terminal 85.

    The way I see it, you can get by with only one relay instead of two. In your diagram, wire both the 12v input wire from the fuse panel and the 12v + wire from your brake lights to the 85 terminal on the one relay, but place a diode between the 85 terminal and the brake 12v + wire so that current can only flow to the 85 terminal and not backfeed to the brake 12v + wire when the 12v current from the fuse box is fed into the circuit.

    Once you sort out the wiring at the switch, it will work.
     
    #7 xliderider, Mar 16, 2016
    Last edited: Mar 16, 2016
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  8. Justdidit

    Justdidit LVNPZEV

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    Good catch, i just ordered this as the local store didn't have anything small like what I wanted, only large trucker parts. Figures.. I live in Alberta.

    5X Amber LED DOT Light 12V CAR Auto Boat Round Rocker ON OFF Toggle SPST Switch | eBay




    merged.



    I saw several diagrams that showed this setup but I wasn unclear as to what diode to get exactly...this dual relay setup allowed me to do the same with no diode.. or so i thought.
     
    #8 Justdidit, Mar 16, 2016
  9. Dion Kraft

    Dion Kraft Member

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    I think this will work with one relay. You can wire in the relay thru the 87a and 30 and not disturb a thing. Just grounding toggle switch and two 12v inputs.
    Changeover_relay.png Changeover_relay.png
     
    #9 Dion Kraft, Mar 16, 2016
  10. Justdidit

    Justdidit LVNPZEV

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    Does it matter what type of 5pin relay? This is interesting, never saw any diagrams for this method using two 12v inputs. Why would u need two?
     
    #10 Justdidit, Mar 16, 2016
  11. Dion Kraft

    Dion Kraft Member

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    The 87 type relay uses 86-87 as a switch. One or the other can be 12volts or ground - doesn't matter. When the coil is energized it throes the lever so 87a and 30 become disconnected and so 30 connects with 87. You need 87 to have 12 volts to power your reverse light. 86 does not connect inside the relay to the power loading side which is 30 to 87a and 87. Hope this answers your question
     
    #11 Dion Kraft, Mar 16, 2016
  12. xliderider

    xliderider Senior Member

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    This will work, IF the aux LED light bar doesn't draw too many amps off the oem reverse light circuit. If I am reading the circuit correctly, when in normal reverse mode and the toggle switch is Off, the only power source for the auxilliary LED lightbar is the oem brake circuit. A second relay would be needed to draw power from the battery or alternate source.

    Using a small diode (1N4001 or 1N4004), which costs a few cents will allow the OP to wire as described in post #7 above with one relay, with power for the aux LED lightbar from the battery, not the oem brake circuit.
     
    #12 xliderider, Mar 16, 2016
  13. Justdidit

    Justdidit LVNPZEV

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    Appreciate the help thus far, but since I already purchased the two relays and it currently works when the car is in reverse, the only thing left is to find out why the switch isn't working. Once I get time, I'll try a switch that is rated for 12V DC and not 120V AC.

    Thank you for everyone's input!

    60F_zps9008ecb8.jpg

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    -2PC Mounting Brackets
     
    #13 Justdidit, Mar 16, 2016
    Last edited: Mar 16, 2016
  14. Dion Kraft

    Dion Kraft Member

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    AS I see it if 87 has a big enough wire to load the switch into 30 upon toggle why not just hook the lightbar on to pin 30 so as not to use OEM b/u wires at all. Of course the b/u light will be on when using the lightbar. Upon rereading the OP's post I thought he wanted the b/u light to be independant using a toggle to switch on/off. MY BAD! But your right we don't want to burn up any OEM wires here as that would probably cost more than this add-on lightbar setup is worth!
     
    #14 Dion Kraft, Mar 16, 2016
  15. 69shovlhed

    69shovlhed Surly tree hugger

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    you got a 60w light and a 5a fuse? 12V x 5A = 60W. you might try a 7.5A fuse
     
    #15 69shovlhed, Mar 16, 2016
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  16. valde3

    valde3 Senior Member

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    Power for the lights is not going through that fuse. 5A fuse only supplies power to coil of that one fuse. There is no fuse drawn in that would protect the circuit or the lights.

    There has to be wiring problem (or the second relay is faulty) because circuit connected in the way that first diagram shows would work. Most likely the wires in your switch are wrong. If they are in wrong order turning on the switch will ground the “12V input” though 5A fuse. Burning the fuse instantly. Ground wire is there for light in the switch?
     
    #16 valde3, Mar 17, 2016
  17. 69shovlhed

    69shovlhed Surly tree hugger

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    valde is right. swap the relays to verify that they are both good. if it works in reverse with the relays swapped, then the switch is definitely hooked up wrong
     
    #17 69shovlhed, Mar 17, 2016
  18. Justdidit

    Justdidit LVNPZEV

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    All valid points. I tried swapping the relays and the reverse still worked. It was the switch.

    I picked up a 12V DC switch, made sure the correct posts were connected correctly and my issue was resolved. No need for diodes...the dual relay with 12v DC two pin switch fixed it all. I was in a electronic store and just assumed that the switch I bought was automotive because I was in the switch aisle where the automotive switches were and someone had put the switch on the wrong peg. My mistake for not looking over my items before purchasing. :rolleyes:

    This is what I ended up with - works great!
    AUX_Reverse_Diagram.jpg
     
    #18 Justdidit, Mar 18, 2016
  19. xliderider

    xliderider Senior Member

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    Glad everything turned out well. :)
     
    #19 xliderider, Mar 18, 2016
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