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Thread: Circuit Question

  1. #1
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    Circuit Question

    I've been testing the various circuits in my SC to try to locate the electrical problem that started the long saga and mess. I've been testing it using this method...

    No battery
    remove one fuse at a time
    test resistance on each side of circuit where the fuse was
    All circuits should be open (i.e. not working) so I should not show any resistance at all.
    One circuit (actually 3 but they're all connected at the power distrobution box) does show resistance. The circuits in question are labelled "I" "J" and "K" and are I-auto shock, J-Ignition switch, and K-Anti-lock module.

    Should this show as a closed circuit when there's no power to the car at all?

    I think it should be like any other circuit and show that it's open. I've been having some other electrical issues that started pointing to the ignition switch as a possible problem, then I had massive electrical issues and it's been parked for over a year and a half now. I've got it back together now and want to track down the problem to its source. After testing the circuits I'm nearly convinced that it's the ignition switch that's causing all my grief. I'm not 100% confident in my electrical ability yet, so I'd like someone else to chime in and confirm my suspisions. Thanks.

    Sam

  2. #2
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    Quote Originally Posted by 007_SuperCoupe View Post
    I've been testing the various circuits in my SC to try to locate the electrical problem that started the long saga and mess. I've been testing it using this method...

    No battery
    remove one fuse at a time
    test resistance on each side of circuit where the fuse was
    All circuits should be open (i.e. not working) so I should not show any resistance at all.
    One circuit (actually 3 but they're all connected at the power distrobution box) does show resistance. The circuits in question are labelled "I" "J" and "K" and are I-auto shock, J-Ignition switch, and K-Anti-lock module.
    Open means Infinite resistance, not NO resistance. Shorted means zero resistance.

    All circuits should have some load on them, otherwise the fuse will blow from the current flowing through a shorted circuit.

  3. #3
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    Quote Originally Posted by Mike8675309 View Post
    Open means Infinite resistance, not NO resistance. Shorted means zero resistance.

    All circuits should have some load on them, otherwise the fuse will blow from the current flowing through a shorted circuit.
    My electrical talk isn't what it could be...you know what I meant, obviously.

    No fuses blew, but the fuseable link on the back of the alternator did. So sourcing the issue becomes more challenging. There's a short somewhere. I've got the battery out, all switches in the open position (that I know about) and that particular circuit goes to "0" on the multimeter.

    What does that mean? To me it means there's a short in that curcuit... I'm strongly suspecting that it's the ignition switch. Does that make sense?

  4. #4
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    What are you measuring? Volts DC, Ohms?

    For resistances (ohms) what does it say when you have the leads not touching anything or themselves? That is what it reads with infinite resistance, an open.

    What does it read when you touch the two leads together? That's a short.

    Verify the switches are doing something by sensing and flipping switches looking for changes.

    Keep in mind that higher load items are going to be driven by relays and require power to operate.

  5. #5
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    Quote Originally Posted by Mike8675309 View Post
    What are you measuring? Volts DC, Ohms?
    Ohms

    Quote Originally Posted by Mike8675309 View Post
    What does it read when you touch the two leads together? That's a short..
    Reads infinite when testing an open circuit...0 when testing a closed circuit.

    It reads 0 when testing the above circuit. The rest are at infinity or the needle moves just slightly. But that circuit is just like putting the leads together.

  6. #6
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    Ok... so which circuit. Above you mentioned 3 or 4.

    I would investigate those that look like they are shorted. Get alldata or a EVTM and follow those wiring circuts to their connectors testing at each connector to see where the issue starts.

  7. #7
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    If you were to open your power distibution box, there are 3 fuses that are a little apart from the rest. They're labelled I, J and K. They are all linked directly together on one side (big metal plate) and on the other side they go to their respective circuits. All 3 test out the same. One is the auto shock (ARC I would guess?) the other the ignition switch, and the last is the antilock module. I've had other gremlens that point to the ignition switch (like the trunk opening when the ignition is "on" and a door is open), so I suspect that's it. I don't have an EVTM. Wish I did, but I don't. If anyone has one on electrons for a '92, I'd love to get one. But as it stands, I'm going to have to do it the hard way. I've just heard that when the ignition switch goes, it wreaks havock on lots of different things but the symptoms vary so much it's hard to pinpoint the problem.

  8. #8
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    That should be somewhat easy to troubleshoot. Disconnect the ignition switch and plug everything back in.

    Is everything behaving? Then plug the switch back in. Does stuff go wrong?

    if so, bobs your uncle.

  9. #9
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    wiring

    i just bought an evtm on ebay for 10.00 shipped. i think i typed in ford schematic. just went to ebay and they list 266 items for ford schematic-good luck

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