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Wiring a three pronged rocker switch

  1. Jul 7, 2010 #1
    Alright, I came here looking for help as I haven't been able to figure out the answer.

    in that picture the left is the bronze colour prong, following two are silver. There are numberings for each prong going 3-2-1 respectively from left(bronze, BUT the bronze pin has both a + and - sign vertically over the #3) to right.

    I'm trying to wire this switch to control a cooling fan on my motorcycle, however, there are only two wires that are present. Obviously, power and negative. I'm trying to have the swtich not only turn on the fan but also illuminate the rocker.

    How do I wire it up.

    Flame away if you must, but at least provide me with the answer.. lol
  2. jcsd
  3. Jul 7, 2010 #2
    Most of those switches are the same. So try this.

    Pin 1 to 12VDC from your motorcycle

    Pin 2 to + input of your fan (tie the - input of the fan directly to ground)

    Pin 3 to ground
  4. Jul 7, 2010 #3


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    Staff: Mentor

    Do you have a DVM or resistance meter? Just beep out the connections. There will be one common pin, and the switch position will determine which one of the other two pins is connected to the common pin.
  5. Jul 8, 2010 #4


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    Science Advisor

    Welcome to PhysicsForums!

    In my experience, I'd assume the bronze one is probably the common, if it's a SPDT (single pole, double throw switch). For the schematic representation of that, see the Wikipedia page:

    The switch looks like it may light up. If it does, the internal wiring of the switch may be different, and one of the contacts may actually be for the lamp. You didn't happen to hang onto the packaging the switch originally came in?
  6. Jul 8, 2010 #5
    I will presume that it _is_ a lighted switch (with an internal lamp of some kind). If you have an Ohm meter, two of the pins will appear to be connected together and will (dis)connect from the third when you toggle the switch. That third pin is the one that should go to the +power. The two that seem to be connected should actually have a very small resistance between them because one of them goes to the lamp -- and is meant to go to the -power/ground so the lamp lights up when the switch is on. If you can tell which of the two has a slight resistance to the +power-pin when ON, that is the bulb-ground pin. If you can't tell which is which, connect one to your fan (DO NOT connect the other to ground yet) and see if the fan runs. If the fan works and the bulb is not dimly glowing, that is your switch control pin. If no-workie or dim glow that pin is the bulb-ground.

    I would draw a nice schematic but it would take even longer than this description...
  7. Jul 8, 2010 #6
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