Alternator/regulator upgrade

Electrical and Ignition

  1. MungoMopar

    MungoMopar Active Member

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    Hi,
    My '67 Dart is showing very little charge voltage, ~12.2V when off, ~12.2V when running and the ammeter sits 3/4 the way toward full charge on the right hand side (~30A ?).
    The car starts ok, although it's only used in the daytime in good weather so not much electrical load. I'm wanting to sort this out as it's not ok to always have that high current showing; I'm not seeing the normal high charge after starting that gradually reduces as battery charges.
    The car doen't have the voltage regulator on the bulkhead, it's been modded at some time. The alternator is a square back with I'm guessing an aftermarket voltage regulator attached to it, picture here.
    IMG_1731.JPG
    The alternator has 2 field terminals, one red wire from the stud terminal to a field spade and one green wire that may come out of that chrome box. Aftermarket regulator?

    I'm needing suggestions on what route to take please.
    How would you deal with this set-up?
    I haven't yet but I will check the voltage at the terminal with the green wire (field excitation?). I suppose that either the alt or reg could be bad.
    Would you keep this set-up and replace whatever is needed with the same parts?
    Is there a preferred make and model of aftermarket voltage regulator to attach to the alternator?
    Reinstate the original regulator type?
    To replace this 2 spade terminal alternator, I would buy a later 73-74 Dart item?
     
  2. Lord Sparky

    Lord Sparky Well-Known Member

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    I went with Powermaster one wire a few months ago. So far, so good. Check Crackedback for headlight relay harness and alternator to starter relay wire. Get rid of ammeter. Powermaster made me an alternator ground wire.
     
  3. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    You may be jumping too soon. The readings you posted contradict each other. The ammeter should not be showing that much charge with that little battery voltage. Maybe the battery has a dead cell or is just wornout 'bad" or is nearly dead. Very first thing to do is try to charge the battery and have it load tested......but a real load tester, not some "pocket" instrument

    Next thing I'd do is get it running and up on "fast idle" to simulate low-to medium cruise and RE check battery voltage and then measure voltage at the big output stud on the alternator. Maybe a big voltage drop in the harness is causing the low reading. Both the battery and the output stud should be within maybe a volt of each other

    If you happen to have another "easily removed" known good 12v battery I'd swap that in and see if there is a difference

    That alternator is basically a 70' and later Mopar incorrectly called "dual field." Correctly it is "isolated field. Someone like Powermaster has added an on board regulator to turn it into a functionally "one wire" alternator I believe.
     
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    • MungoMopar

      MungoMopar Active Member

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      Lord Sparky
      Thank you, I'll check the Crackedback's wire options.

      67Dart273
      Thank you for focusing me on determining the problem rather than working out where to source each spare part in the system.
      I did some testing; while running at idle the battery voltage across the terminals was 12.6V and from the negative post to the alternator output stud was 14.6V.
      I then borrowed the battery off my son's '72 Satellite and these two voltage measurements were pretty much the same again. I didn't get around to raising the revs to cruise level, I'll get another set of hands to help with that. Neither battery has been tested, I'll get the Dart battery done to be sure of condition.
      I checked voltage from battery positive to alternator stud and it shows a volt drop of 1.9-2.0V as expected (14.6-12.6=2.0). This is suggesting too much resistance between battery and alternator?
      Looking at the wiring diagram, the two heavy wires on the alternator stud run to the horn relay (purple) and to the ammeter (black), is that correct reading of the diagram?
      There isn't a direct wire from alternator to battery?
      Is this where the discussion on bulkhead connector condition comes in?
       
    • 67Dart273

      67Dart273 FABO Gold Member FABO Gold Member

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      2v from alternator stud to battery+ is getting to be a bunch. "The path" is alternator stud---through bulkhead connector(big black)--through underdash welded splice---through ammeter----back out through bulkhead (big red)---through fuse link and underhood wiring to battery.

      This is the functional path not necessarily direction of electron flow. Each point--and each terminal at each point is a suspect and it could be more than one.

      The 14.6 is fine at the alternator--shows it is regulating at a proper setpoint

      The output stud of the alternator also feeds off to the horn relay--merely a junction point
       
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      • Mattax

        Mattax Just the facts, ma'am FABO Gold Member

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        If it helps visualize the current path, on a factory '67, it would look like this after starting.
        basic-charge-circuit-charging-animated-gif-gif.gif

        As you know, once the battery is recharged, the ammeter should be around zero for normal driving.
        I'd look for resistance in the output path and then the battery line.
        upload_2021-6-10_8-50-59.png

        Also look for anything to the battery side of the ammeter that might be drawing current through the ammeter.

        upload_2021-6-10_8-57-13.png

        Since the charging circuit has been rewired, one of the things to do is figure out how that was done.
        You can start with this and fill in as you figure it out. The only items originally on the ignition run were the ignition and the alternator.
        upload_2021-6-10_9-4-19.png
         
      • 67Dart273

        67Dart273 FABO Gold Member FABO Gold Member

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        I tend to divide the charging system into sections----no particular order

        Output circuit. On an OEM car this is the path from alternator output stud to battery, so wire terminals, through the bulkhead, welded splice, ammeter, back through bulkhead, fuse link, etc to battery. On a car that is NOT a "one wire" set up you can stand some voltage drop in this circuit as the regulator will just keep ramping up, but that may affect other circuits in the car, and exaggerate damage to already damaged terminals, like the bulkhead connector

        Field circuit. This is the path from battery, ammeter, igntiion switch, back through the bulkhead on the "igntiion run" (ign1) circuit, to the VR, and on 70/ later, the blue field wire. Voltage drop here is very important because any drop is ADDED to the charging voltage THIS IS BY FAR THE MOST common single problem in these girls, voltage drop in this circuit. Adding a relay is an easy way out

        VR...VR MUST be grounded to same potential as battery, the connection at the removable connector (70/later) must be good and tight, and of course VR must be properly functional

        Alternator. On isolated field units (70/later) make certain neither brush is shorted to case WHICH HAPPENS with rebuilds Make certain pulley belt is not loose/ glazed/ misaligned etc, or that pulley ratios are not so far out of whack that it will not spin fast enough. Most alternators do not output fully until the alternator shaft is up around 5-6K RPM

        Problems with alternators include the mentioned field short, or an internally PARTIALLY shorted field, one shorted or open diode, or a stater that is shorted between turns. Speed up RPM at night, watch inside alternator. If you can see a "micro lightning show" in there and it is NOT the brushes, you have insulation rubbed off the stator, and the windings are vibrating together, shorting out
         
      • MungoMopar

        MungoMopar Active Member

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        Mattax and 67Dart273 thank you for describing the potential charging fault locations.
        I will take another look tomorrow; I'll strip back the harness branch to the alternator and try and see what was done in the stock reg delete mod. I checked the bulkhead connector a few months back and in was in good shape; I'll check it again to ensure that it's still good (not caused by my intervention).
         
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