Voltage drop at ballast resistor

Discussion in 'Electrical and Ignition' started by Paladin06, Apr 5, 2018.

  1. 67Dart273

    67Dart273 Well-Known Member

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    THAT is the biggest clue yet. You very likely have a bad terminal (connection) right there a the bulkhead connector, either between the two terminals, or between one terminal and the wire it's connected to
     
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    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

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      Good. 13.24 Volts brings up the battery's surface charge. The reason the voltage goes down at each point you measured is probably entirely due to the surface charge dissipating.

      This must be a typo or a bad reading.
      As we expect. So far so good - except if that Alternator output connection reading is real - which the only way it could be is if its a loose connection and got worse when probed. Does that make sense? Everything in the main run should be at battery voltage.

      Main_charging_wires_Test-Off.png
       
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      • Paladin06

        Paladin06 FABO Gold Member FABO Gold Member

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        This must be a typo or a bad reading.

        This reading was at the bulkhead under the hood.
         
      • Paladin06

        Paladin06 FABO Gold Member FABO Gold Member

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        This the red wire to the amp meter.
         
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Good.
        I've put this on the drawing...
        They're fine. Lets look at what they show.
        12.1 Volts at the battery under a 5 amp load. OK. especially seeing the next reading down the line.
        12.2 Volts at Starter Relay.
        11.8 Volts at Bulkhead. 0.4 Volt drop in the wire is a lot. If real, could be a bad crimp connection at either end or the fusible link splice, (corroded or broken strands ).
        11.5 Volts on both sides of the Ammeter and at the Alternator connection. No loss to speak of from the battery wire to the main splice. (Since there is no load and no current in the black wire to the alternator - it can not be assumed the alternator's bulkhead connection is good.)
        10.5 Volts at Run. Must be resistance between the main splice and this connection.

        Sounds like a loose connection or a wire with bad insulation? Is the red wire is the one from the main splice to the ignition switch?
        If that's warm with just 5 amps, that's a major problem.

        Main_charging_wires_Test-On.png
         
        Last edited: Apr 17, 2018
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        Well something isn't right. Can't have 13 volts at the Alternator stud and battery but just 1.4 volts at the bulkhead connection.
        If its real, something is loose and making intermitant contact. Or worse, there is a chafed wire and its grounding. But if was shorting on the main splice side of the ammeter - you'ld see the ammeter bounce to higher discharge whenever it contacted.
         
        Last edited: Apr 16, 2018
      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        You found a small voltage drop in that section. Very much agree the heat is a big clue. 5 amps in that wire should not heat it any more than the other 10 and 12 gage wires.

        I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
        Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

        Same thing with the blue run wire connector and terminals. The drop you found there is even worse. Problem(s) also could be at the start switch, or worst case, the main splice. So check the whole run.

        Does that make sense?
         
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        • halifaxhops

          halifaxhops It's going to get stupid around here! FABO Gold Member

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          :popcorn::popcorn::popcorn:
           
        • zkx14

          zkx14 Duster De-ruster FABO Gold Member

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          48A6916D-EEED-4A6D-BE62-67172FC7E161.jpeg
           
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          • Paladin06

            Paladin06 FABO Gold Member FABO Gold Member

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            Please explain below:
            I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
            Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

            Under the hood on under the dash?
             
          • Paladin06

            Paladin06 FABO Gold Member FABO Gold Member

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            OK with the switch on and bulkhead connector removed as I said earlier I get 11.8 volts at the blue wire with fusible link. If I disconnect the fusible link from the red wire leading from the starter relay I get the same voltage reading as the battery. Bad fusible link maybe? What tool is required to remove the pins from the bulkhead connector. I want to replace the fusible link.

            Thx again.
             
          • Mattax

            Mattax Just the facts, ma'am FABO Gold Member

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            Where ever the voltage dropped when current was run through it. Ignoring whatever variations there are in the readings, there was a .5 Volt drop between the relay and the whereever you read it on the bulkhead, and another .3 Volt drop to the ammeter. Since that wire is warm its more suspect.

            Then there's a 1 Volt drop between the Ammeter and the run wire connection at the bulkhead.

            The .4 Volt drop to the alternator's stud makes no sense unless there's a short inside. If there was a short inside, it should have shown up in the measurements with the ignition off.

            Main_charging_wires_Test-On-result.png
             
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            • Paladin06

              Paladin06 FABO Gold Member FABO Gold Member

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              Disregard this last comment. The voltage is the same through the fusible link to the bulkhead connector. Been messing with this thing since 0700 this morning. My back is killing me. Going to take 2 oxy and chill.

              Thx all.
               
            • Paladin06

              Paladin06 FABO Gold Member FABO Gold Member

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              After cleaning the corroded fusible link connection I now have the same 12.3 volt reading at the bulkhead connector, the starter relay and the battery.
               
            • Paladin06

              Paladin06 FABO Gold Member FABO Gold Member

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              I have no reading at the alternator stud or the wire at the bulkhead connector.
               
            • Paladin06

              Paladin06 FABO Gold Member FABO Gold Member

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              E459ADB1-2EA2-4DB7-B6B6-468F4AA4A9C2.jpeg Couldn't sleep a wink last night so I got up and studied this thread from the beginning. A couple of questions.
              1.With the four pole ECU do I really need the four pole ballast resistor? I was told some years ago on this forum I did not. This is what my resistor looks like today.
              2. Most diagrams provided and the shop manual show the red wire from fusible link to the bulkhead connector. My fusible link is tapped into the bulkhead connector, with the red wire at the starter relay to the fusible connector. Is this an issue?
              3. Does anyone have a DYI or know of a video for replacing the ignition switch?
               
              Last edited: Apr 17, 2018
            • 67Dart273

              67Dart273 Well-Known Member

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              • 67Dart273

                67Dart273 Well-Known Member

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                2....Can you re--describe this? Or photo? Can't "get" what you are trying to convey

                All you are doing, here, is providing power from the starter relay stud---which is also a junction point "battery"..........through the fuse.........to the bulkhead. There may be minor variations over the years about the wire "makeup."
                 
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                • Paladin06

                  Paladin06 FABO Gold Member FABO Gold Member

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                  I’m sorry did you read through the thread? The issue is trouble shooting voltage drop at a number of locations
                   
                • 67Dart273

                  67Dart273 Well-Known Member

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                  I don't understand what you are trying to describe with the fuse link.....what is the suspected issue with the physical wiring? Your statement


                  "2. Most diagrams provided and the shop manual show the red wire from fusible link to the bulkhead connector. My fusible link is tapped into the bulkhead connector, with the red wire at the starter relay to the fusible connector. Is this an issue?"

                  is what I don't understand
                   
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                  • Mattax

                    Mattax Just the facts, ma'am FABO Gold Member

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                    I don't understand either.
                    "most diagrams provided" If you mean what I posted here - those are by Nacho and the wire colors should just be considered generic.
                    The only one that is likely to be completely correct, is the one in the service manual for your year. If you have, post a picture of the it becuase I don't have '72 FSM in print or digital.
                    But in the photo above, the harness has been modified - certainly the connectors changed and at least one wire taped off or ? So it looks modified. What else is modified?

                    "tapped" In this context, its generally understood as a side tap. Often the quick and dirty squeeze type connectors. Maybe Del reads it the same way. Its very confusing.
                     
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                    • Paladin06

                      Paladin06 FABO Gold Member FABO Gold Member

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                      Gentlemen I’m sorry if I confused or upset any of you. You help is so much appreciated and I am forever greatful. We will get Cherry fixed and I will have you all to thank. Due to physical limitations I have to go slow and the pain meds do take their toll. I just ask that you hang with me. We will get there.

                      Thx

                      Greg A
                       
                    • 67Dart273

                      67Dart273 Well-Known Member

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                      Quite all right. I'm partially disabled at 69, myself, with arithritic like conditions, and in particular, neck problems. "Crawling around" under a dash is VERY tough on this old guy

                      The last several "gist" of what you have posted indicate that it's all "right there" in/ at the bulkhead connector or the under-dash harness. Might be time to find a (younger LOL) local friend/ help to help pull the cluster and access things.

                      I waste no time........I pull the seats!!!!
                       
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                      • Mattax

                        Mattax Just the facts, ma'am FABO Gold Member

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                        So you disagree. It is confusing on my end.
                        Take your time. Underdash is never fun. Leaning over the fender gets to me too after a while.
                         
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                        • Paladin06

                          Paladin06 FABO Gold Member FABO Gold Member

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                          Now to top it off I been in bed two days with the flu .