12v Illuminated Switch with switched neg circuit

Discussion in 'General Electronics Chat' started by Aqua, Apr 19, 2009.

  1. Aqua

    Thread Starter New Member

    Apr 19, 2009
    2
    0
    Hi there,
    I've searched all day (and every link that Google could give me) for a concise answer to this question. Hopefully someone here can help me.

    I have a 12 volt illuminated rocker/toggle switch that I'm trying to hook up to a 12 volt dome light. Actually, it is hooked up and the dome light is working- what I can't seem to find an answer to is: how to make the light illuminate inside the switch.

    The switch is a standard one with 3 terminals to connect to Power, Load and Earth/Ground. I know that if it were not the lighted type, it would have just 2 (power and load) as the ground is for the light. (BTW, I'm not sure if the light is incandescent or LED- I suspect the former due to the large side of the 'window').

    Pretty simple so far, right? The curveball is that the circuit is a switched-ground. To be clear on what I mean, the positive wire connects directly to the dome light (the light is always hot) and then comes out and goes to the switch, which connects to ground. (i.e. if you take the wire coming out of the light and short it to earth, the light works).

    I've tried just about every combination- one of which allows the switch's internal light to illuminate when the dome light is OFF (not what I want).

    My thinking is that when the switch is closed (dome light on) the current, upon reaching the switch, takes the path of least resistance which is NOT through the circuit that lights the tiny lamp, going instead directly to ground. Perhaps if I were to attach a small resistor (with greater impedance than the switch's lamp) to this ground wire, perhaps it would work??? Or do I need a relay?

    I know there are lots of people that have tried wiring negative-switched items with illuminated switches, so there is an easy answer, I'm sure.

    Oh, and I want to do this without using a power source external to the vehicle (i.e. I don't want to power the switch's light from a 9 volt battery)- it must be from the vehicle itself.

    Can anyone help? :)
     
  2. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    If I understand you correctly, you were required to hook up the light switch downstream of the light. If you have a diode(LED), you will need to reverse the wires to the switch. if the diode is reversed, it won't light.
     
  3. Aqua

    Thread Starter New Member

    Apr 19, 2009
    2
    0
    Yes, the switch is downstream of the dome light. No- it's not an LED- just a regular incandescent.
     
  4. bundick

    Active Member

    Dec 19, 2007
    97
    1
    In my lighted switches in the house, that third wire is the ground circuit for the light.
    So when the light switch is on, the ground is ignored and the Light in the switch is not on.
    When you turn the light off, then the current flowes through your light in the switch, to the grounded terminal.

    Clear as mud eh?
     
Loading...