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Thread: Custom Electrical System

  1. #1
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    Custom Electrical System

    More electrical work complete - I've now got a cool, completely new scratch-built electrical system, exclusive of the dash, which is next.

    PDF of my schematic is 380K; I can e-mail to anyone interested.

    Forrest
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  2. #2
    Senior Member MacGyver's Avatar
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    Re: Custom Electrical System

    Nice and organised. It's a shame to cover it up behind a body panel.

  3. #3
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    Re: Custom Electrical System

    Thanks!

    At least it will be visible every time I fold the rear body section forward to fuel up or show off.

    Forrest
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  4. #4
    Senior Member AdrianBurton's Avatar
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    Re: Custom Electrical System

    I would like to see it....
    burtona -at- consultant -dot- com

    I am a sparky, what can I say??? ;D

  5. #5
    Senior Member MacGyver's Avatar
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    Re: Custom Electrical System

    Quote Originally Posted by McDesign
    Thanks!

    At least it will be visible every time I fold the rear body section forward to fuel up or show off.

    Forrest
    absolutely!

  6. #6
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    Re: Custom Electrical System

    I would like one please! hmdznrcld@comcast.net


    TIA

  7. #7
    Senior Member rodrieguz's Avatar
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    Re: Custom Electrical System

    I'd Definately like to take a look @ that pdf, rodrieguz@hotmail.com

  8. #8
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    Re: Custom Electrical System

    Hey - I'm happy that schematic might get integrated into someone else's project!


    Here's a teaser I'm noodling about now - just trying to be satisfied with the
    answer, as a practicing engineering nerd.

    Okay - I'd like a big external switch near the battery (probably at the base of
    the windshield) that shuts off the entire electrical system, and kills the
    engine. Simple, right? Tons of switches like that available.

    Ahh - not really.

    Lets say I buy the common, 2-terminal, 500-1000 amp (momentary) SPST switch.
    One side is attached via a short wire to the battery, the other side, the ouput
    side, to the starter solenoid and the rest of the electrical system. What about
    the charge wire from my 1-wire alternator? Hey - I'll just hook it to the
    output side of the switch also.

    Whoops! Now when I turn off the switch with the engine running, the alternator
    keeps powering the electrical system and the engine; it keeps running (and
    without the moderating load of the battery).

    Okay, that's fine, I'll just connect the charge wire to the BATTERY side of the
    switch. Now when I flip the switch, the alternator and the battery are both
    disconnected from the electrical system, and the engine shuts off - cool. BUT -
    now I have a big 6-8 gauge wire with a 150-Amp Maxi-fuse going back to the
    alternator that's still "live", even with the main switch "OFF".

    Ah - I know what you're thinking, "Forrest, just get the darned 4-terminal DPST
    switch (two independent switches controlled by one lever), advertised by
    everybody and their brother, that's MADE to also disconnect the alternator."

    Hey - that sounds good - BUT - that secondary contact set is only rated for 20
    amps - not sufficient to constantly carry the charging output of a 140 amp
    alternator, much less break the running circuit more than once or twice without
    welding the contacts. All switches are like this - the Moroso, the Flaming
    River, the Longacre, the Summit house brand . . .

    Turns out, that 20-amp capacity circuit is made to cut off the FIELD wire to a
    3-wire alternator ONLY. There is no solution when using a 1-wire alternator.

    Well, I THINK a solution for me is to use the 4-terminal switch, but this way.
    Hook the battery to one side of the main contact pair, and the alternator and
    rest of the electrical system to the other side of that contact pair. Then, use
    the secondary contact pair to interupt the ignition wire from the ignition
    switch - kill the engine that way.

    So - engine running, when you flip the switch, the battery is isolated, and the
    ignition (and thus the engine) shut off. As the engine coasts down, the
    alternator is briefly powering the rest of the electrical system, until the rpm
    drops low enough that the alternator charge function to drop out - a couple of
    seconds.

    I do have the relay logic set up so that the fuel pump can't operate with the
    ignition off, so it's immediately off.

    It's the best I can come up with. Any better ideas?

    Forrest - rambling


  9. #9
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    Re: Custom Electrical System

    Buttoned up and cranked this evening!

    Here's the main battery switch - about 18" from battery post to the switch (it's a sealed DPST Longacre unit). Coming off the switch goes to a bulkhead terminal post (the red cover). Inside the car is the main battery cable going back to the starter, as well as to a 100-amp Maxi-Fuse fusible link, for the power to the front of the car.

    The secondary set of contacts interrupt the ignition switch signal going back to the MSD box in the rear.

    Also, on the hot, "always on" side of the battery switch, is a little "cheater" wire with an immediate 2-amp fuse in a little weatherproof pod for my dashboard clock.

    Forrest
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  10. #10
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    Re: Custom Electrical System

    First pic is the (24)-position terminal strip for the wires coming from the rear of the car - it's mounted on the left side of my footwell, where the door hinges mount.

    Second pic, you can see the inside of that bulkhead terminal. Attached to it are the black starter cable, the red 6-gauge charge wire from the alternator, and a short red 2-gauge wire to the left, to the black Maxi-Fuse housing. Coming out of the left side of the Maxi-Fuse are three red 10-gauge wires - one to the headlight relays, one to the electric fan relays (and the horn relay), and the third to power the dash. These wires aren't arranged prettily yet - that will happen when I make the new dash.

    Forrest
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