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Thread: What's going on with my Generator?

  1. #1
    Member Nemo von Klepper's Avatar
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    What's going on with my Generator?

    This is my first time messing around with a generator, so essentially my first rodeo. The regulator is new from KW and the generator was just rebuilt, all 12v.
    It doesn't seem to be charging:
    Volt meter with the engine at about 1000rpms reads 12.2 and gradually sinks to 11.9. I was expecting somewhere around 14. I made sure the polarity was set, momentarily jumping the battery to the armature tab on the regulator (type A generator). I got a spark, a hum and the generator turned for a second the same direction as the engine. I considered this to be a good sign that the generator is in fact good. I noticed right before I turned the engine on that the amp meter which has been stubbornly been at zero was now marking at -50 amps. After I turned the engine on, the amp meter went back to just on the positive side of zero but I was only able to read 12v with the volt meter.

    Next I took the lid off of the regulator. Everything there looks good, shiny and new.

    I'm not sure what to do next.

  2. #2
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    My generator experience is pretty limited and I don’t know at what engine RPM these generators need to produce power. I know on applications I am familiar with 1,000 rpm isn’t likely to get the generator generating. Usually 1200-1500 to get them started and they fall off line at 800-1000 but there are variables that can make up the difference. Most notable is the pulley sizes.
    Jeff
    '51 CJ3A
    '47 CJ2A

  3. #3
    Member Nemo von Klepper's Avatar
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    Ok, so the old timers are probably rolling their eyes about now, "Here we go with the 'My generator isn't charging' conversation again!"
    Yup, you said it. A brief search over the internet yields many, many conversations on this subject, almost exactly like my conversation. So tomorrow I'll try it again at a much higher RPM. I expect it'll be fine, which will be a relief since I decided to rebuild the generator instead of an alternator at a likely higher cost. At least someone gave me the generator core. I want to get this rig on the road this summer so I'm chomping at the bit to move on to getting the brakes adjusted and start rolling.

  4. #4
    Super Moderator bmorgil's Avatar
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    We need LarrBeard to pipe in here but, I would be looking at the regulator. It might need adjustment.

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    Super Moderator LarrBeard's Avatar
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    What’s wrong with my generator?

    Quote Originally Posted by bmorgil View Post
    We need LarrBeard to pipe in here but, I would be looking at the regulator. It might need adjustment.
    Herr von Klepper:

    We “Old Guys” don’t mind answering the “Why isn’t my battery charging; what’s wrong with my generator?” questions. It makes us feel like we’re still important! Here is more than you probably want to know....

    Disconnect the Field lead from the generator (at the generator case), that would generally be the smaller of the two terminals. Since you have a rebuilt – donated – generator, make sure you have Field and Armature figured out correctly.

    You are going to ground the field terminal; by doing this you are going to bypass all of the relays and resistors in the voltage regulator and put the generator at close to full output. The most conservative way is to make up a test lamp (12-volt tail light bulb), hook one lead to a good frame ground and with the motor running, connect the other to the Field terminal. This allows a bunch of current to flow through the Field windings. The bulb should light up (it should be pretty bright) and you should get a + reading on the ammeter. This connects the light back to the battery through the Field windings and brushes, but limits the current through the Field coils to what the lamp would normally draw. (An 1141 bulb will draw about an amp or a little more – it might not bring the generator to full output, but it will give you an idea if things are alive).

    The other less conservative way is to just take a clip lead and ground the Field terminal directly. This will put a LOT of current through the Field windings, so do not hold it too long or magic smoke will come out of somewhere, usually the insulation of the clip lead. This should put you at a hearty + reading on the ammeter – full output of the generator. Really old timers called this “full fielding” a generator.

    This should give you an idea of your generator’s ability to turn RPM’s into amps. If you don’t get amps with these tests, I suspect an issue with the generator. If these checks give you amps, I’d replace the regulator. Defective (but new) voltage regulators are rare but not unheard of. Adjusting one is almost never necessary and it takes a lot more “stuff” that most of us want to fool with these days.

    Good luck, let us know what you find – and we’ve not seen any pictures of the project lately.

  6. #6
    Member Nemo von Klepper's Avatar
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    Well, anymore anyone is an old timer if they learned to drive on a stick, type on a typewriter, dial a rotary phone, etc.

    3F55E669-D28F-4325-AAD5-7E4326555886.jpg

    I’ll take a look today when I need a break at work. Thanks for the input.

  7. #7
    Member Nemo von Klepper's Avatar
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    Well, tear it all! Yesterday afternoon when I went to try the jeep, the battery was completely flat with no obvious cause: headlights, blinkers, etc. It was too flat to even jump it by myself, so I've had it on the charger all night with the negative post disconnected.

    Not sure what's going on now. Before I tried to re-polarize the gen the day before it was seemingly not charging, might be user error, but it also wasn't draining the battery. Not sure at this time if it's related, I might have just run the battery down too much when I was messing with it before.

    Before I reconnect the battery, I'm going to check for an amp draw between the negative post and the cable. If that exists, I'll try to isolate the source: Check for continuity between the positive post on the battery and the field or armature posts on the gen, or voltage at the gen with the engine off. If those exist, then I'll check for continuity between the battery terminal and the field or armature terminals on the regulator.

    My theory here is that one of the contacts on the regulator maybe stuck, creating an electro magnetic field in the gen., but then I don't know much about generators.

  8. #8
    Member Nemo von Klepper's Avatar
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    Ok, so now it might be charging, but my ammeter is going crazy. Related but separate issue so posting in a new thread.

  9. #9
    Super Moderator bmorgil's Avatar
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    Nemo it does sound like the regulator is having fits. Larry might jump in here with a circuit diagram. It sounds like the contacts in the cutout are having an issue.

    Here is a good Voltage regulator 101.

    http://www.secondchancegarage.com/public/83.cfm
    Last edited by bmorgil; Today at 07:09 AM.

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