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Thread: Where to wire to

  1. #1
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    Where to wire to

    I am putting this under power supplies because it is power-supply related. I'm not sure if there is a better spot for it.

    In my car, Subaru pre-wired a connecor under the dash which is essentially a carputer enthusiasts wet-dream come true. It has power, IGN, ACC, Vehicle speed, backup light and various other circuits all in one nice little plug.

    I am thinking that the easiest thing to do would be to connect the carputer into this.

    The BATT+ wire is fused at 7.5 amps and appears to be 16 AWG wire although I am not sure. There is also a vehicle ground wire in this connector.

    My Atom based carputer pulls less than 3A and will be installed quite far away from the eventual distribution block for the audio system.

    What, if any, are the drawbacks to using this connector to power the carputer? Can the carputer's power supply safely be connected to the ground lead in this connector or should it be grounded somwhere else? The carputer's audio connector will feed audio equipment that will be grounded elsewhere.

  2. #2
    Neither darque nor pervert DarquePervert's Avatar
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    Quote Originally Posted by sebberry View Post
    The BATT+ wire is fused at 7.5 amps and appears to be 16 AWG wire although I am not sure. There is also a vehicle ground wire in this connector.

    My Atom based carputer pulls less than 3A and will be installed quite far away from the eventual distribution block for the audio system.

    What, if any, are the drawbacks to using this connector to power the carputer? Can the carputer's power supply safely be connected to the ground lead in this connector or should it be grounded somwhere else? The carputer's audio connector will feed audio equipment that will be grounded elsewhere.
    Your best bet is to ground all your audio equipment at the same point.

    And if that connector is 16awg, I wouldn't use it for the PC, even a low-power Atom-based setup.
    While it is possible that the wiring could handle the load, I wouldn't trust it. It's safer to run new wires so you are 100% certain of their load-bearing capability.
    Have you looked in the FAQ yet?
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    Quote Originally Posted by DarquePervert View Post
    Your best bet is to ground all your audio equipment at the same point.

    And if that connector is 16awg, I wouldn't use it for the PC, even a low-power Atom-based setup.
    While it is possible that the wiring could handle the load, I wouldn't trust it. It's safer to run new wires so you are 100% certain of their load-bearing capability.
    Thanks for the input. I'll have to check the guage to be sure. Why would it be fused at 7.5A if a 3A load is risky?

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    Neither darque nor pervert DarquePervert's Avatar
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    Quote Originally Posted by sebberry View Post
    Thanks for the input. I'll have to check the guage to be sure. Why would it be fused at 7.5A if a 3A load is risky?
    The fuse is there to protect the wires, not the equipment.
    Have you looked in the FAQ yet?
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    Quote Originally Posted by DarquePervert View Post
    The fuse is there to protect the wires, not the equipment.
    Thanks, I understand the point of fusing to protect the wires.

    What I am saying is if the wires aren't capable of handling 3A for the carputer, why would Subaru fuse it at 7.5A?

    (Not trying to question your experience, just trying to understand why it would be unwise to use a factory installed connector which appears to be there specifically for aftermarket equipment).

  6. #6
    Neither darque nor pervert DarquePervert's Avatar
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    I don't know whether that wiring harness is capable of a 3A load or not.
    You don't know, either. If you did, you wouldn't have asked.

    So rather than take guesses, you are better off running your own power wires that you know beyond the shadow of a doubt will handle the load you will put on them.
    Then there will be no question whether your wiring is sufficient.

    If you use the existing fused circuit and the wiring is not sufficient, then you have the situation that 2K1Toaster has made famous with his awesome MSPaint skillz:
    Have you looked in the FAQ yet?
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  7. #7
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    Darquey - you have been told...
    .... that I like that drawing...
    (And I needn't applaud "fusing is for the cable" etc etc ....)

    Quote Originally Posted by sebberry View Post
    What I am saying is if the wires aren't capable of handling 3A for the carputer, why would Subaru fuse it at 7.5A?
    Maybe because 6A or 7A is used for something else?

    Most seem to want to provide their own supply for things like 'putors & audio straight from the battery (through a fuse or circuit breaker, and maybe through a relay). I do!
    This is to ensure adequate supply that is independent of vehicle systems.

    It is usually simpler than researching the vehicle's system.
    And is is the next step if you find that using existing wiring has problems.
    (And it should not effect vehicle warranties etc.)

  8. #8
    Neither darque nor pervert DarquePervert's Avatar
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    Quote Originally Posted by OldSpark View Post
    Darquey - you have been told...
    .... that I like that drawing...
    I take no credit for that drawing. That is all from 2K1Toaster.
    I just make sure that it is used appropriately, and as often as possible.

    And I must say that I love it, too.
    Especially the way the guy's eyes are bugging out when his car is on fire.
    Have you looked in the FAQ yet?
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  9. #9
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    Quote Originally Posted by OldSpark View Post
    Maybe because 6A or 7A is used for something else?

    Most seem to want to provide their own supply for things like 'putors & audio straight from the battery (through a fuse or circuit breaker, and maybe through a relay). I do!
    This is to ensure adequate supply that is independent of vehicle systems.

    It is usually simpler than researching the vehicle's system.
    And is is the next step if you find that using existing wiring has problems.
    (And it should not effect vehicle warranties etc.)
    I've got all the wiring diagrams, nothing else appears to be on that wire or fuse.

  10. #10
    Raw Wave
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    Then it is your decision.

    If it is 16AWG, you should only have ~0.04V per meter drop (at 3A load), plus whatever other path resistance/drops there are including the ground path.

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