wiring/electrical question
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This is a discussion on wiring/electrical question within the Interior Mods forums, part of the Tech & Modifying & General Repairs category; ok if i tap into an existing wire in the cabin to get power for my gauges, do i need ...

  1. #1
    Moderator Penguinking's Avatar
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    wiring/electrical question

    ok if i tap into an existing wire in the cabin to get power for my gauges, do i need to get a resistor or somethign? since I = V/R, and (R) in a parallel circuit (which is what it would become if i split the wire, right?) is inversed, ie now the ohmage is = 1/R.

    if i'm right about this, then wouldn't i have to keep going to the positive end of my battery and be continuously adding wires to it to get power? that would sure make things cluttered
    Silver 911
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    Registered User WRXed's Avatar
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    Re: wiring/electrical question

    Originally posted by Penguinking
    ok if i tap into an existing wire in the cabin to get power for my gauges, do i need to get a resistor or somethign? since I = V/R, and (R) in a parallel circuit (which is what it would become if i split the wire, right?) is inversed, ie now the ohmage is = 1/R.

    if i'm right about this, then wouldn't i have to keep going to the positive end of my battery and be continuously adding wires to it to get power? that would sure make things cluttered
    I think that you're overanalyzing this. You should be fine just splicing into a "power" wire. "ohmage" - I love that!
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    Registered User Shadow's Avatar
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    Re: wiring/electrical question

    Originally posted by Penguinking
    ok if i tap into an existing wire in the cabin to get power for my gauges, do i need to get a resistor or somethign? since I = V/R, and (R) in a parallel circuit (which is what it would become if i split the wire, right?) is inversed, ie now the ohmage is = 1/R.

    if i'm right about this, then wouldn't i have to keep going to the positive end of my battery and be continuously adding wires to it to get power? that would sure make things cluttered
    Penguin,

    WRXed is absolutely correct, you are overanalyzing this. However, I will use my Electrical Engineering knowledge to answer your question.

    Ohm's Law, V = IR, will not be violated if you use an exsisting wire to power your gauges. It's "almost" like using one of those 3-way outlet things in your house. You can convert one outlet into three by simpy plugging in the 3-way adapter. The thing to keep in mind is the current, not the resistance. You are simply splitting the +12V wire in two, which means that the current that can be drawn be either device has dropped by one-half. Your setup will work just fine as long as you don't run a hairdryer or portable toaster oven off the wire you tapped.

    Happy splicing.

    -Shadow
    2002 Subaru Impreza WRX Sedan 5MT - Midnight Black Pearl
    2009 Subaru Impreza WRX Wagon 5MT - Dark Gray Metallic

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    Moderator Penguinking's Avatar
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    hmm....so the current is dropped in half? so what happens as i add more...say, make it into a 3-way adaptor? does that mean all the devices from that wire only get 1/3 the ampage? id think that would cause your center console to dim, or not work, if its only getting 1/3 the power its supposed to have.

    btw, i thought it was the voltage that gets divided, not the ampage.





    ...sorry if im making this too complicated, but i want to understand this stuff as good(well?) as possible so i can save time trying to set up wires and stuff to power gauges and such in my car
    Silver 911
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    i believe what shadow is trying to tell you is, that you can tap into your 12volt source and get the correct voltage you need... but you must be concious of how much current that wire needs to provide to its original device and how much you will need it to provide to whatever you may be adding....otherwise you will have fuse problems or worse....

    example...tapping into your main power in your ignition harness to power a radar detector or alarm is okay....but to power a stereo amplifier is just not going to work because that wire cannot provide enough current...

    just examples!!!!! hope that helps!
    Last edited by schmecky; 10-23-2002 at 11:48 AM.
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    now onto '03 wrb wagon!!

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    Registered User Shadow's Avatar
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    Originally posted by schmecky
    i believe what shadow is trying to tell you is, that you can tap into your 12volt source and get the correct voltage you need... but you must be concious of how much current that wire needs to provide to its original device and how much you will need it to provide to whatever you may be adding....otherwise you will have fuse problems or worse....

    example...tapping into your main power in your ignition harness to power a radar detector or alarm is okay....but to power a stereo amplifier is just not going to work because that wire cannot provide enough current...

    just examples!!!!! hope that helps!
    schmecky,
    What you said is true, and it was the main point I was trying to make.

    Penguin,
    The voltage does not get divided. If it did then how would household outlet splitters work? It is VERY IMPORTANT to remember that the voltage remains constant, and the available current drops. Tapping a wire to hook up your gauges should be okay. But tapping it more than once could cause you some problems.

    -Shadow
    2002 Subaru Impreza WRX Sedan 5MT - Midnight Black Pearl
    2009 Subaru Impreza WRX Wagon 5MT - Dark Gray Metallic

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    Moderator Penguinking's Avatar
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    lol, i think i'll just stop asking questions and go w/ what you guys have said - i thought i was right, but then what i really meant to say was resistance and not voltage, but when i said that i meant current really, but then i remembered you had already said that, and then i just went cross-eyed thanks for all the help guys; if i do happen to mess up w/ the wiring, i doubt i'll do that much damage
    Silver 911
    WRX's older brother

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