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NooB Question - 12V wiring switch circuit

  1. Dec 8, 2008 #1
    Hello all,

    I am stuck in a rather simple, yet confusing quandary..

    I'm working on designing a light kit for a Honda side x side utility vehicle. We are planning on drawing power from the back of the existing cigarette lighter auxiliary outlet on the instrument panel, and running the power to a simple ON/OFF switch to turn the driving lights on and off.

    The question that I have is rather simple, or maybe it's just a case of the 'Mondays', but frankly, I'm quite lost... The cigarette lighter is only rated at 15amps, therefore, because we will be drawing power off the back of the cigarette lighter auxiliary outlet, we will have to ensure that the outlet is disabled when the driving light switch is turned ON.. and when the driving light switch is turned OFF, the auxiliary outlet will be re-enabled. How can something like this be achieved??

    We will be using 2x 55w driving lights (9.17amps).. If that helps any.

    I would really appreciate any and all help as soon as humanly possible!!!!! Ahhh, monday's suck!! :)

    I look forward to my future here in these forums.. looks like ya'll have a good group here! :D

    Attached Files:

  2. jcsd
  3. Dec 8, 2008 #2


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    You need a single pole double throw (SPDT) switch.
    Disconnect the 12V line to socket and connect it to the input on the switch
    Then connect one output of the switch back to the socket and the other output to your lights.
    Then the switch selects between socket or lights.

    Check the power rating on the switch - make sure it is rated for 15A.

    You might want to to put an inline fuse before the switch - I'm always suspicious of the wiring for aux sockets, they tend to be done very cheaply since most people only use them for ipods/cell phones.
  4. Dec 8, 2008 #3
    That's awesome.. exactly what I was looking for!!! Thank you so much for your help sir! :)

    See, I knew it just had to be a case of the Mondays.. haha

    Now for the fuse before the switch, should a 15A be fine then??

    Gosh, thanks so much again! :D
  5. Dec 8, 2008 #4


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    Yes 15A is fine and is a standard car size
    In theory the aux socket will be fed form a 15A fuse - but you never know.

    There might be better ways to do this - there might be a spare line on the regular fuse panel for fog lights or extra lights fitted to a higher spec model. But if you want to take the power form the aux socket, that is how I would do it.
  6. Dec 8, 2008 #5

    Great! Thanks again for your help, I greatly appreciate it! :D
  7. Dec 8, 2008 #6
    Can i ask you for one more favor please?

    Is there anyway that you could draw up a simple circuit diagram for me explaining the wiring?? I'm terrible on Monday's, I swear!!! haha :D :D
  8. Dec 8, 2008 #7


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    Something like this.
    You might want to disconnect the battery before you start - but make sure you have alarm/radio unlock codes first.

    Attached Files:

  9. Dec 9, 2008 #8
    Awesome!!!!! That is exactly what I was looking for! :D :D :D
    Would the 15A fuse go between the SPDT switch and the socket, or would it be on the 12V power coming into the SPDT, then channeling off to either the lights or the socket? I think now I've got a case of the Tuesdays!!!!!!!! lol
  10. Dec 9, 2008 #9


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    You generally want to put the switch as close to the supply as possible,
    If you put it before the switch it protects you from anything too powerful being connected to the aux socket or the lights pulling too much current.
    Remember you need to connect it somewhere where you can get at it.

    The power line to the aux socket should already be connected to a fuse in the regular fuse panel - try and check what fuse is there. There is no danger in having 2 fuses in series, but you won't know which one has blown.
  11. Dec 9, 2008 #10
    Great! Thanks again so much for all of your help... Honestly, sometimes the really simple things get me all confused, but quite frankly, I'm a complete noob at electrical engineering, hence why I majored in Mechanical.. hahaha :)

    What is your name btw???!

    Thanks again!!!!
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