Alternator not charging

Discussion in 'Electrical and Ignition' started by partsman1965, Apr 26, 2018.

  1. partsman1965

    partsman1965 FABO Gold Member FABO Gold Member

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    Looking for help! My 74 Dart sat all winter indoors and when started for first time this spring
    alt charged for short bit then stopped. I have done the following.
    New Alternator since old one was making noise anyway
    New regulator
    New ballast..4pin
    New ground battery cable
    Refreshed all grounds to body and engine.
    I have the wiring diagram and have found no bad wires yet! I have not yet checked wires as they go through firewall. Anyone know which wires through firewall allow alt to charge?
    Main power feed from amp gauge has good connection through firewall.
     
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    • j par

      j par Well-hung Member

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      Do you have a free Harbor Freight voltmeter?
       
    • j par

      j par Well-hung Member

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      And I hope you bought the regulator that was a couple dollars more and not the really cheap one cuz that could be your problem right there. But again we need to start with the cheap Harbor Freight voltmeter. Or any voltmeter for that matter.
       
    • j par

      j par Well-hung Member

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      High School auto shop A1A just because you bought a new part does not mean it works.
      (RIP Mr. Kingham)
       
    • partsman1965

      partsman1965 FABO Gold Member FABO Gold Member

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      I got a Standard brand regulator. I also have a good Craftsman voltmeter.
       
    • j par

      j par Well-hung Member

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      So in this situation I put the voltmeter on and check the volts from the battery. I continue right there checking the volts and have the wife crank it over and start it and notice how much it drops while cranking? Then of course what it's doing while it's running? Did it go up did it go down did it stay where it was at?
       
    • j par

      j par Well-hung Member

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      Sometimes you'll see it bouncing up and down and that's the regulator opening and closing.
       
    • partsman1965

      partsman1965 FABO Gold Member FABO Gold Member

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      Thank you!
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      Read this so you have a good idea how the circuit works.
      Understanding Charging Systems with Ammeter

      On yours, the blue wire feeds the alternator's field and the green wire controls the connection to ground completing the circuit. So the blue will connect with voltsage regulator and the ignition 'run' side junction on the ballast resistor. This is how the regulator knows the system voltage. It regulates by opening and closing the circuit's connection to ground.
       
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Field is another name for the electomagnet that spins. The windings create an magnetic field when powered up.

        Here's a general diagram of the later charging systems like yours.

        Main_charging_wires_plus.png
         
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        • AJ/FormS

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

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          You can prove your alternator CAN work by full-fielding it. You run a jumper from the battery plus to the field terminal, and then ground the second terminal. You will connect the ground, with the engine running, the battery recently charged and a VOLTmeter previously installed across the battery, and all accessories turned off..Alt output must be higher than battery rest voltage by at least 1.25 volts, and increases with rpm. Do not go crazy with rpm, you might blow the ignition module. If it makes the minimum, consider it to be ok.

          I connect the ground last while watching the voltmeter, and as soon as I see the voltage, I disconnect the ground. In this way I prevent damage to sensitive components. The charge circuit itself will happily work at 15.5 volts, and mine has withstood 17 volts on occasion. But the headlights didn't.
           
          Last edited: Apr 26, 2018
        • 67Dart273

          67Dart273 Well-Known Member

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          Post 11!!^^

          But in addition, test for an open from battery to alternator output

          Hook up as above, and with the jumper connections made, slowly bring up RPM and see if battery voltage rises

          If not, move your meter to the alternator "big stud" (output stud) and see if that voltage rises and if so, to a high level. If it does, then you have a bad connection in the circuit from output to battery

          If neither meter connection shows a rise, attempt to determine if the field is actually drawing current. With the engine off, and "in the shade" preferably darker, hook/ unhook your connections to the field. You should be able to see a small spark every time you connect the jumper.
           
        • partsman1965

          partsman1965 FABO Gold Member FABO Gold Member

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          Found it! Black ammeter lead at firewall was not making good connection!
           
        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

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          Black ammeter lead goes to the firewall?? Typically red goes to firewall bulkhead; black goes to main junction. Alternator output is generally Black 12 gage and goes from firewall to main splice.
          Each year is a little different so that's why I say generally. You may be right.
           
        • AJ/FormS

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

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          That location is often the root of charging issues, and the fat red one in there as well.
           
        • 73beast

          73beast Active Member

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          Found this thread on a search, and thanks for the info!
          Solved my charging issue, had a bad connection at the firewall bulkhead connector. Mines a black wire from the alt to the bulkhead, was a cooked/corroded connection.
          Will bypass when I find a decent passthrough connector, just cleaned it up for now
           
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          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            Depending on your goals, one option is to use no connector. Put a ring terminal on the alternator stud, run a heavy black wire through a grommet in the firewall. If done in parallel to the original wire it can be attached with a ring terminal to the alternator side stud of the ammeter. Otherwise splice into the original alternator feed to the main splice as long as its a very good splice.
             
          • Kendog 170

            Kendog 170 Member

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            Some remove the wire from bulkhead connector and drill right thru with drill bit that makes a snug fit. Then as said feed wire through and add your ring terminals.