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Electro-philes: crit a 280Z HL diag.

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    First and foremost, I appreciate your persistence in the effort to offer constructive criticism. Thank you.

    Editorial sidebar:

    However, as the Man once said, "what we have here is a failure to communicate". The first issue is mine, as my old eyes have great difficulty in distinguishing the colors in which your stick-figure diagram is rendered. Add to this that one cannot distinguish a connection from a crossing and, for me, confusion has its head.

    And frankly, the decision to use your own line colors instead of those in the diagram we are actually discussing, doesn't promote clarity. So I hope you will understand that my comments will always reference those colors in my presentation diagram.

    While I can understand feeling a need to dumb things down enough for the challenged to get your point, I would again submit that your simplifications are too extreme and at the cost of relevant details.

    But, to work.

    Off the top, I have two big clouds of fog that obscure my vision of truth:

    Fist is wonder how you consider the relay coil to be in series in the feed flow from both headlights. While I have often felt my ignorance is boundless, I have long thought that I know a parallel circuit when I see one, like, as shown in your first diagram, and in mine. Again, when two circuits start and stop at the same points, is this not a parallel circuit? I would maintain that your garage experiment did not replicate the situation accurately.

    Second, for the life of me, I cannot grasp this business of disappearing current once the coil is energized. The feed presents the same voltage for both legs at the Y, and both legs of the parallel circuit possess the same potential current differential to ground, yes? This one stumps me. Of course, I designed it as a parallel circuit...

    Perhaps clarity would come from you addressing just these two issues, should you still be inclined to help.

    Here's something else I don't know (the list is getting long, eh?): how big is the window of voltage tolerance for a typical 12v relay coil? Does it vary with the number of contacts?

    By the by, are we in agreement about the Power relay being workable as shown?

    Nice math; shows a laudable dexterity. No sense in quibbling about the assumptions, like that the coil is in series and on only one headlight circuit. I don't think the corrections would change the fundamental issues here.

    Now, I don't mean to be a difficult student, but I'm getting a feeling that your not really reading my homework.


    Keep those cards and letters coming folks. Like the clown at the dunk tank, I'll take all shots, as long as you hit the bullseye of addressing the topic/approach at hand.


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    1st - You have series and parallel elements in the way you drew up your circuit. I have spent many years reviewing controls drawings for work, and I have studied the wiring diagrams for S30s for over 25 years. I can recognize a good and bad circuit design.

    2nd - The current doesn't disappear. Your circuit is designed wrong. You have the coil in SERIES with the headlight, AND you have the coil in PARALLEL with your path to ground. 

    I read your stuff. You don't understand what you're doing. When I can wire up a circuit per your design and it doesn't work, I think that proves it. You have not shown a workable circuit. If you think you have, wire it up and prove me wrong. Spoiler: You won't prove me wrong.

    Click here

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    When you put that way....  

    I don't want to seem ungrateful for the properly explicit analysis, but you could have saved us both a lot of verbiage, if you had said as much 3 or 4 posts ago. But hey, better late than never.

    Clearly, I am painted into a very tricky corner. Well, if at first you don't succeed...  it's back to the drawing board.

    While I do not yet know how to best use this information, it does make clear the wisdom of getting input from those whose understanding of some complex situation exceeds one's own.

    I'd like to thank you Mr.J (and all that generously offered something helpful) for your patience and expertise.

    But as a man once said, "I'll be back".

    Call it a fetish.


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    I did say those things in my first response on this thread. I cannot help it if you are too obtuse to absorb it.

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    Sorry I didn't meet your standards.

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    And it seems somehow my previous input was overlooked as well.

    In response to your request, I posted a bunch of ways people have successfully installed headlight relays.

    So in case something went wrong with the previous message and the info did not come through on your screen, here they are again. Here's hoping whatever went wrong with the message last time works this time:









    HRelay Kit.JPG




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    Posted (edited)


    You can put your hand down Mr.Obvious; we saw them the first time. I'm sure they're fine solutions in their own right, but as none meet the critical criteria of my particular project goals, they are still of no interest to me.

    To Work:

    Plan C

    This iteration taps the nearby feed from the fusible links to provide a switchable and unencumbered source for the Secondary Relay's coil. I believe this resolves the previous issue of contention. The question is, are there more in the wings.

    The area of change is highlighted on the detail below.

    WrngDiag_6 det 1.jpg

    Edited by ensys

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