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Thread: well, the darn thing is out

  1. #751
    Super Moderator gmwillys's Avatar
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    It was a thought. I know I've seen where someone put out a video about the steering column bearings, but do not remember quite were I saw it. I'll poke around and see if I can come up with anything.

  2. #752
    Senior Member pelago's Avatar
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    the two bearings inside pretty straight forward bu the column??

  3. #753
    Senior Member pelago's Avatar
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    I think either the generator or voltage regulator went south, voltmeter only reading battery

  4. #754
    Super Moderator gmwillys's Avatar
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    Have you full field the generator, and measured at the generator. LarrBeard had laid out the process better than anyone, so he can chime in and post.

  5. #755
    Super Moderator LarrBeard's Avatar
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    Quote Originally Posted by gmwillys View Post
    Have you full field the generator, and measured at the generator. LarrBeard had laid out the process better than anyone, so he can chime in and post.

    Getting to the armature and field on an M38A1 generator is a pain if you have to fish in the connectors, but it is the same process. Put a lantern battery on the field, spin the generator and check armature (with no load on generator). Probably well over 50 volts in a 24-volt system.

    I would not count out a wire problem since its been charging OK for a while.

  6. #756
    Senior Member pelago's Avatar
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    i disconnected the wire going to voltage regulator. not sure which is which simple 3 connector plug. started engine up and got low voltage across field and winding way low, but not sure if that is correct test. maybe i got lucky though, there is a electric shop here and the owner appears to be comfortable with old cars and is a admirer and likes to work on "old stuff" and did find a "repair" kit on ebay that has all (think) pieces and parts on ebay

  7. #757
    Super Moderator gmwillys's Avatar
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    The 24 volt system is harder to troubleshoot, because all the connectors are sealed. When you disconnected the connector, you will see that the voltage is low. With the connector unhooked, then the regulator is taken out of the equation, thus the generator doesn't produce but a standby amount of voltage. There are some service kits that come up from time to time on Ebay, that the government had produced for troubleshooting all gas fueled military engines. The kit includes T harnesses that hook into your regulator harness so that the voltage can be measured while hooked up. The kit includes a 24 volt timing light, and instructions.

    Your local electrical repair shop should be able to get you pointed in the right direction. He sounds like he knows his way around a generator.

  8. #758
    Super Moderator LarrBeard's Avatar
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    Here is a reprint of my "Full Field" instructions for a 12-volt system.

    On the M38A1, the ARM terminals are A and C in the generator connector, For this test, you only need one of them. FIELD is B. Even with the regulator disconnected, you will get some voltage from the ARM terminal from residual magnetism in the field pole pieces. The case is ground.


    Full fielding a generator is a term used to describe the process where you drive a bunch of current into the field coil to see just how much voltage the generator will produce. The voltage output of a generator is regulated by limiting the current going into the field coil.

    There are a lot of ways to do this, but here is a way that is pretty safe and won't damage anything.

    Go get a big square six-volt lantern battery - the kind with spring contacts.

    You will need a couple of jumper leads to connect it to the generator. You are going to use this battery to provide current to the generator field coil to create a magnetic field in the generator. The lantern battery won't deliver enough current to damage anything. Connect the NEGATIVE terminal to the generator ground terminal.

    Disconnect the field and armature leads from the generator. The ARMATURE is generally the larger of the two insulated terminals, the FIELD is the smaller. GROUND or NEGATIVE is the screw into the generator frame.

    Connect a voltmeter to the armature terminal of the generator. If it's a manual voltmeter, set to read about 50-volts (you can adjust later). Start the vehicle (generator is turning). Connect the POSITIVE terminal of the battery to the generator's FIELD terminal.

    You should get a significant voltage reading on the voltmeter. Vary engine speed and the voltage should vary - higher speed, higher voltage. Don't be surprised at 35 or more volts on a 12-volt system - that's why you disconnected the ARMATURE terminal on the generator; 35-volts doesn't do batteries or bulbs any good.

    If you get the high voltage from the generator, you have pretty well proven that the generator is working.

    I don't like to full field a generator using the vehicle battery because it can deliver LOTS of amps into the field coil. The lantern battery will current limit itself below damage level.

    Don't run at the high voltage too long, just satisfy yourself that things work. It is not out of the question that the "new" voltage regulator is defective. We had a new regulator fail when we were doing the '48 (another oh-by-the-way) and we used this process to isolate whether the 70-year old generator or new regulator was the problem.

    If the generator checks OK - I'd replace the regulator after I checked all of the wiring.

    Let us know what you find.Full fielding a generator is a term used to describe the process where you drive a bunch of current into the field coil to see just how much voltage the generator will produce. The voltage output of a generator is regulated by limiting the current going into the field coil.

    There are a lot of ways to do this, but here is a way that is pretty safe and won't damage anything.

    Go get a big square six-volt lantern battery - the kind with spring contacts.

    You will need a couple of jumper leads to connect it to the generator. You are going to use this battery to provide current to the generator field coil to create a magnetic field in the generator. The lantern battery won't deliver enough current to damage anything. Connect the NEGATIVE terminal to the generator ground terminal.

    Disconnect the field and armature leads from the generator. The ARMATURE is generally the larger of the two insulated terminals, the FIELD is the smaller. GROUND or NEGATIVE is the screw into the generator frame.

    Connect a voltmeter to the armature terminal of the generator. If it's a manual voltmeter, set to read about 50-volts (you can adjust later). Start the vehicle (generator is turning). Connect the POSITIVE terminal of the battery to the generator's FIELD terminal.

    You should get a significant voltage reading on the voltmeter. Vary engine speed and the voltage should vary - higher speed, higher voltage. Don't be surprised at 35 or more volts on a 12-volt system - that's why you disconnected the ARMATURE terminal on the generator; 35-volts doesn't do batteries or bulbs any good.

    If you get the high voltage from the generator, you have pretty well proven that the generator is working.

    I don't like to full field a generator using the vehicle battery because it can deliver LOTS of amps into the field coil. The lantern battery will current limit itself below damage level.

    Don't run at the high voltage too long, just satisfy yourself that things work. It is not out of the question that the "new" voltage regulator is defective. We had a new regulator fail when we were doing the '48 (another oh-by-the-way) and we used this process to isolate whether the 70-year old generator or new regulator was the problem.

    If the generator checks OK - I'd replace the regulator after I checked all of the wiring.

    Let us know what you find.

  9. #759
    Senior Member pelago's Avatar
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    what would i need for 24vdc, two batteries in series??

  10. #760
    Super Moderator LarrBeard's Avatar
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    All you need is the 6-volt lantern battery. You are using the battery to drive current into the field coil of the generator and make a magnetic field. The generator is going to run in an unregulated mode just to see that it makes a voltage when it spins. It will be an unregulated voltage that varies with engine speed. A 12-volt generator can deliver about 35-volts open loop with no control of field current. A 24-volt may go way above that ... 50?

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