Alternator question

Discussion in 'Electrical and Ignition' started by 4spdragtop, Aug 20, 2018.

  1. 4spdragtop

    4spdragtop FABO Gold Member FABO Gold Member

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    I'm trying to decipher an intermittent charging/starting problem. Before I get too in depth, quick question.
    Should there be voltage when measure from battery +ve to case of alternator? I did quick continuity chk and was surprised, so I measured and I'm getting 12.2 with everything hooked up but car off.
    I'm thinking alternator is shorted internally?
    Anyone?
    67 barracuda SB MP elec ignition
    Thanks
    Steve
     
    Last edited: Aug 26, 2018
  2. 67Dart273

    67Dart273 Well-Known Member

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    Your terminology lost me, Steve. The case of the alternator should be grounded. The output stud is essentially "the battery" so with one meter probe on case, and the other either on battery + or the alternator output stud, you should see battery voltage

    Continuity from case to battery NEG should be zero or close to it

    You still have the factory bulkhead/ ammeter, or has that been bypassed?
     
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    • Frnknsteen

      Frnknsteen FABO Gold Member FABO Gold Member

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      Are you saying you are checking for voltage, and are putting one lead of the volt meter on the + battery terminal and the other on the frame of the alternator? Or are you saying you are using the continuity tester between battery + post and case of alternator, you are getting continuity (i.e. it beeps)?

      If checking voltage, then yes,... that's what you should be getting (12 volts). The case of the alternator should be grounded, so when you touch the red lead of the meter to battery + post, and the negative lead to the alternator frame, you should see 12+ volts on the meter.

      Look at it this way,... your meter actually is measuring voltage difference, so when one lead is connected to power (12 volts) and the other to ground (0 volts) it reads 12 volts (12 volts - 0 volts = 12 volts)

      If checking continuity,.... then no, you should not see continuity between the battery + post and the case of the alternator. If you are, then something is shorted. Just to clarify,... on a typical Fluke (or other brand) electronic volt/ohm meter, when you put it on Continuity checker and touch the leads together, it beeps.

      In the attached picture of a Fluke meter, the red circle is setting to check DC voltage. The yellow circle is the continuity tester setting.

      Fluke.jpg
       
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      • 4spdragtop

        4spdragtop FABO Gold Member FABO Gold Member

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        Sorry guys, I ain't the easiest student. I am getting intermittent continuity/beeps when I put one meter lead on case and one lead on stud.
        Mad bypass has been done. Voltmeter/power dropped out on me twice last night. 2nd time was for good, 2hr fn tow home cuz I didn't bring proper spares.
        Fn electrical....
        Thanks
         
      • 67Dart273

        67Dart273 Well-Known Member

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        The thing is, if your battery is healthy you should be able to drive it a LONG time with just the battery. Night of course will be less, you won't make it 2hrs on headlights. But with no lights you should be able to drive most of a day if you don't stop and restart the engine very much

        So far as fixing it, what do you have? You still have the older (69/ earlier) single field connection, or the newer (70/ later) so called "dual field" (two field connections?)

        Might just be bad brushes. First thing I'd do is rig power to the field and see if it charges.
         
      • 4spdragtop

        4spdragtop FABO Gold Member FABO Gold Member

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        Here is alternator, approx 3yrs old(reman) Green wire attached to field, black wire and purple wire to batt stud.
        Retro looking vr, but modernized inside.
        Should the small hex nut(between field terminal and stud) have a ground wire?
        Thanks.
        20180820_163412.jpg

        20180820_132750.jpg
         
      • Dana67Dart

        Dana67Dart Most undignified way to get to Colorado!

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        Since the alt is out can you bring it to a parts store that has a tester?

        If memory serves me that is the grnd brush no external wire attached.

        Some of the diodes seem too deep in the housing. Most I have seen they are flush.

        upload_2018-8-20_16-18-56.png upload_2018-8-20_16-19-33.png
         
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        • 67Dart273

          67Dart273 Well-Known Member

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          Steve you can make some simple tests right on the car. That is for certain the older 69/ earlier setup with a replacement regulator

          I would pull the brushes and examine them and the slip rings, for dirt, grease, how worn (short) they are. They should be under spring tension

          Rig a jumper wire from the battery to the field connection on the alternator. Run the car while watching battery voltage on the meter. It should start to climb, but don't let it go much above 15.5 or so, control with throttle. Turn on headlights, re-adjust RPM it should "keep up."

          If it charges unsteadily it might be a bad brush, brush connection, or might be in the wiring path between alternator and battery. It could also be a stator "rubbed raw" (insulation rubbed off) as well as a bad diode. This is inferring the intermittent condition.

          To eliminate the charge wire path, jumper a heavy wire direct from the alternator stud to the battery. Repeat the test. If the intermittent goes away, check the output wiring.

          If it still jumps, comes, goes, or won't charge, time for another alternator
           
        • 4spdragtop

          4spdragtop FABO Gold Member FABO Gold Member

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          Ok even more confused now. So this is a 67 style alternator, MP elec ignition and 70+ style vr?
          No tester at parts store.
          I agree those " things" appear to he sunk in a bit.
          Now with alternator out of the car there is no continuity between alt case and batt stud.
          Sorry frustrated as fuck, I was hoping for a quick test on this alternator. Always something fuckin electrical with this bitch.
           
          Last edited: Aug 26, 2018
        • Dana67Dart

          Dana67Dart Most undignified way to get to Colorado!

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          Those "things" are the diodes.
          upload_2018-8-20_17-11-24.png
           
          Last edited: Aug 20, 2018
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          • 67Dart273

            67Dart273 Well-Known Member

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            Regulator.........no it is an electronic VERSION of the old style.........exactly what belongs on there for a replacement

            There should not be continuity with the + probe of the meter on the stud and the neg probe on the case. "I think" if you turn the leads around there will be continuity. All that would show, if continuity in both meter lead directions, is that it is shorted, but the smoke and fire LOL would have already told you that. YOU REMEMBER that problem, doncha? LOL?

            WHAT YOU would be trying to accomplish:

            By feeding the alternator field and running on the car, you are just trying to run down what it might be. By feeding the field power with a clip lead, you are eliminating all the field wiring and the regulator.

            By jumpering direct from alternator stud to the battery, you are eliminating all the wiring between.

            If it still jumps around or charges and quits, or doesn't charge, THEN at that point you can be sure it's the alternator

            REPLACEMENT: If you don't care so much about "restore correct" appearance, the 73/ or so and later alternators so called "square back" are a better unit. They have two field connections, all you need to do is ground one and hook it up like your old unit.
             
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            • Murray

              Murray FABO Gold Member FABO Gold Member

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              Am I missing something? It looks like you have the original alternator set-up (excepting solid state VR). The one spade connector at bottom, near mounting, is hot and leads to VR, while the other brush terminal is grounded. It looks like you may have it insulated. The insulating washer under the screw head belongs under the other terminal. Just be sure that this terminal is grounded.
               
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              • 67Dart273

                67Dart273 Well-Known Member

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                Good eye
                 
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                • 4spdragtop

                  4spdragtop FABO Gold Member FABO Gold Member

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                  Thanks guys, I'm at work, so I will answer as much as I can.
                  Bear with me here. The alternator is approx 3 yrs old. Bought from Canadian Tire, I can't find receipt to verify 100% what application I gave them.
                  I know that it was a direct bolt on, I did no mods to it.
                  Del, yes I remember the "burnout" from 2012...like it was yesterday lol.
                  I replaced the VR last year(black case upgraded guts) see earlier pic, or 2 years ago.
                  A quick rundown of how I got to this point. Driving home from Moparfest, doing approx 65 Mph, all of a sudden no power at all, basically car shut off. Quick 3 lane change, pull over. I wiggle this n that, turns over but no start. After 1/2 hr of trying a couple things, it fires up! Starts but VOLTMETER(Mad amp bypass done) is reading approx 11.5 volts??
                  Get back on highway.....65 MPH. Keeping an eye on all the gauges. Volt is gradually creeping up to 15 Volts. Took about 10 minutes to get to 15.
                  Got about 20 minutes of driving, then no power again.(I'm getting good at 3 lane changes by this point).
                  This time no start....2 1/2 hours on side of the road trying(Im a stubborn prick).
                  Towed home.
                  Next morning I wake up, swap ECU. Starts right up.
                  Pull around to back yard to see if I can figger it out.
                  Wont start again. I tried "tap test" with key on everything hooked up except the electronic dist plug, no spark.
                  I threw a cover on it walked away and went fishing instead....more fun pouring catching Walleye and Bass lol.
                  ALL SUGGESTIONS WELCOME lol
                  67 Barracuda, MP elec ignition, Mad bypass, VR is old style with electronic guts( I believe). Alternator is single field old style( I believe)
                  Thanks again guys I plan on tackling this Monday and Tuesday, so any tests/results I can do I will.
                  Thanks!
                   
                • Murray

                  Murray FABO Gold Member FABO Gold Member

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                  Good info- this is a challenge. When you say it quits and no power, does this mean no starter either? Or does this mean the engine quits, the starter turns over, but the engine won't start? I am leaning toward over-heating coil on one and bulkhead connector on the other.
                   
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                  • 4spdragtop

                    4spdragtop FABO Gold Member FABO Gold Member

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                    Sorry, I knew I was forgetting something. Of course I had 2 spare coils with me on the side of the road, but no spare vr or ecu. I tried a spare used coil....no change. I didn't want to make a ton of "changes" as that would make it harder to isolate the problem.
                    My last attempt to start, I stuck a test light in spark plug boot, key on, jumped starter relay, no light at test light.
                    Oh to answer your question lol, it cranks over.
                    I was thinking a "heat" issue as well, whether ecu or vr.
                    Thanks Murray.
                     
                  • Daves69

                    Daves69 Well-Known Member

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                    :thumbsup:
                     
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                    • RAT ROD AL

                      RAT ROD AL FABO Gold Member FABO Gold Member

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                      Steve here is my simple solution to the ALT problem. I hate elec. issues too. Screenshot_2018-06-27-15-05-38-1.png
                       
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                      • 4spdragtop

                        4spdragtop FABO Gold Member FABO Gold Member

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                        Lol yep, Al that is/was me! I envisioned the alternator going thru the windshield! Both front and back lol.
                        Lol Dave, that was sposed to say "pouting", not "pouring" damn phone. Although yes I did do some pouring as well as pout lol.
                        I'm thinking the way the voltmeter slowly climbed that its NOT the alternator?
                         
                      • RAT ROD AL

                        RAT ROD AL FABO Gold Member FABO Gold Member

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                        Some times thats the best thing to do is put it up, walk away and go back another day after chilling out and thinking it out . With all the help here you'll get figured out.
                         
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                        • 67Dart273

                          67Dart273 Well-Known Member

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                          You likely are on the wrong track with alternator/ charging problem, Steve. With a car an a "good battery" you should be able to disable the alternator and still drive the car........even with lights........at least 1/2hr to an hour. In the daytime a LONG time.

                          You likely have trouble in the bulkhead connector.........ammeter connections........ignition switch connections.......or cough gag.........the welded splice in the harness. You say, "no power" did you have anything at all? If not, then it's not the ignition switch.
                           
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                          • 67Dart273

                            67Dart273 Well-Known Member

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                            This is one reason I often post the MAD article.......it has a decent simplified diagram:

                            Catalog

                            amp-ga18.jpg

                            The main power distro goes.............battery.........starter relay.........fuse link.........bulkhead connector (the big red)........ammeter.........through the meter........out on the big black..........to the WELDED SPLICE which is a few inches from the ammeter on the big black............branches off from that and feeds headlights, hot accessory buss, ignition switch,............etc

                            So if you have NO power there is very little between that and the battery
                             
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                            • 4spdragtop

                              4spdragtop FABO Gold Member FABO Gold Member

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                              Del when it happened it was on the highway both times. So I'm not sure. Kinda panic mode with cars all around lol.
                              I wanted to get it fired up and "wait" for it to die and investigate.
                              To test alt, should I remove field wire from alt or battery wire?
                              I will look into the bulkhead connectors.
                              I did the Mad bypass, but I can't remember if I got "rid" of the welded splice?
                              Thanks Del, square peg round hole with me and electrical...better grab a bigger hammer lol.
                               
                            • Daves69

                              Daves69 Well-Known Member

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                              Had that issue with mine Steve.
                               
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                              • 4spdragtop

                                4spdragtop FABO Gold Member FABO Gold Member

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                                2 of the 3 engine side harnesses are new from MH when we got it in 2012. I had them off last year when I did MAD bypass. All grounds on VR and ECU when I checked it were good.
                                Thanks Dave