Duster fusible link wiring problem

Discussion in 'Electrical and Ignition' started by Dakota Smith, Sep 14, 2018.

  1. Dakota Smith

    Dakota Smith 1976 340 Feather Duster

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    867DA27A-23BB-4E95-AA40-6AE0668E24D8.jpeg My duster isn’t starting now for some reason. There’s some pretty shotty wiring under the hood that I plan on replacing in the near future, but for right now there’s one wire that I figured out is causing a problem. It says “fusible link” on the wire and it’s two bare wires that are wrapped around each other. The previous owner had it like this. Whenever I put the positive terminal cable on the battery it makes an arcing noise and the wire that says fusible link will get hot and smoke. Should I solder the two wires together? The car ran with them like that for months, but now it’s acting like they are hooked up wrong. I did have electrical tape over the wires, but it melted off.
     
  2. AJ/FormS

    AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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    Before you do, go look for a short.
    With the key off, and the lights off including the dome, and the brake sw off, that circuit should be dead. And if it's dead....... there would be no sizzling.
     
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    • TF360

      TF360 Well-Known Member

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      Yearone sells a nice new under hood harness- correct colors and everything
       
    • Dakota Smith

      Dakota Smith 1976 340 Feather Duster

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      That would be perfect because that is the only wiring that is bad in the car. Thank you! I have looked for an engine only wiring harness, but was unable to find one. I can install that in one day.
       
    • AJ/FormS

      AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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      You'll still have to look for a short, or risk frying the new harness.
       
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      • Dakota Smith

        Dakota Smith 1976 340 Feather Duster

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        Wouldn't replacing the wiring harness under the hood fix the short? The wiring is only shotty under the hood. Everywhere else is fine.
         
      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        How can you know unless you test it?
        It could have a short in the bulkhead connector, the column connector, the signal sw or the headlight sw, or the brake lights could be stuck on, or the dome light was on, or the ammeter shorted to the frame, or the alternator is shorted, or a million other things, none of which have anything to do with the underhood harness. And that's just the factory wiring.......
         
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        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

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          It will help you understand why AJ posted that once you understand the main circuits are always hot. No current flows in those wires when the switches are off, but the potential is there. So you just need to figure out what is completing the circuit to ground when hooking up the battery. If the key is off, headlights are off, then it really limits the possibilities. Current is flowing, and it shouldn't be. If the fusible link is not compromised (and it may be from your previous posts) then getting hot indicates a lot of current.

          Read this so you understand how a fusible link protects the unfused wires.
          Fusible Links in Charging Systems with Ammeter
          Shown there is a basic circuit with one fusible link. Once you understand how it works, you can make a similar diagram for your car. This will help you find the short.

          If the diagram here is to be believed, your Duster has two fusible links. Knowing which one (or both) are getting hot will narrow the problem. If that wiring diagram is correct, the power is distributed from two points instead of one main splice used in earlier years. The wire to the ignition switch is spliced in on the engine compartment side and gets its own fusible link. Thats one reason why it looks different than what we typically see here.
          (A factory shop manual diagram is better to rely on than the one in that link. But if it matches what you have in the car, that's great.)
           
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          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            Revised schematic which may better represent '76. The gray represents the 2nd fusible link which you may have.
            Should be helpful in seeing which wires are hot.
            You'll have to mark up for details to match your car.
            Main_charging_wires_plus1976-off.png
             
            Last edited: Sep 14, 2018
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