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Thread: Stator Papers AC on phase and minus battery. 3 times GS 750 '79

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    Default Stator Papers AC on phase and minus battery. 3 times GS 750 '79

    We have an issue with the stator papers, Phase B , the last Test, measuring the ac voltage between one of the three phases and battery (-).
    We have now the third on generator and the first , the second and the third one has about 35 Volt AC on the wires at 5000 rpm.
    Is this meaning we have 3 broken generators or is this test not right?
    I've used the stator papers because the loading Voltage isn't higher then 12,8 (@ Battery)
    When I measure the voltage drop between + Battery and + Rectfier , it results in a 350 mVolts , and the max is 250 mV by the stator papers.
    The cause is the bad connection by the main fuse ( I have used sandpaper but that didn't get a better result.)
    When a short circuit this item the loading voltage is max 13,4 Volt, and that's to low.

    Sorry for the bad language , I'm Dutch and mu English is rusty.

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    "measuring the ac voltage between one of the three phases and battery (-)."

    What is being done here is a check to determine if any voltage during this test is leaking to ground....battery negative. The three phases are wound tightly on the stator core...any winding error or ,more likely fried insulation, lets some voltage "escape" to ground, thereby causing reduced voltage output for charging system. The attached pic shows a stator that I replaced 9 years ago...the pencil points to a burned section. This stator struggled to get a charging voltage of 13 volts @ 4000rpm

    image.jpg
    1981 gs650L

    "We are all born ignorant, but you have to work hard to stay stupid" Ben Franklin

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    Thank you for the reply, what I now understood is that all the 3 Alternators thus are broken.
    That's bad luck , and cost me another 7 euro for a gasket.
    I hope that my second hand shop have some good ones.

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    Quote Originally Posted by PeterBoomhut View Post
    We have an issue with the stator papers, Phase B , the last Test, measuring the ac voltage between one of the three phases and battery (-).
    We have now the third on generator and the first , the second and the third one has about 35 Volt AC on the wires at 5000 rpm.
    Is this meaning we have 3 broken generators or is this test not right?
    As Tom said, we are looking for leakage of the stator at 5K RPM which should be isolated from the chassis,frame, battery ground. Want close to zero volts (no more than 1-2 VAC)

    Quote Originally Posted by PeterBoomhut View Post
    I've used the stator papers because the loading Voltage isn't higher then 12,8 (@ Battery)
    In the Quick Test (see link in signature) I recommend providing 6 voltages so we can diagnose what is going on.

    Quote Originally Posted by PeterBoomhut View Post
    When I measure the voltage drop between + Battery and + Rectfier , it results in a 350 mVolts , and the max is 250 mV by the stator papers.
    The cause is the bad connection by the main fuse ( I have used sandpaper but that didn't get a better result.)
    Voltage drops are mainly due to Corrosion and the biggest problem is in the crimps which can not be helped with sand paper. You need a chemical clean like Vinegar of Naval Jelly. DeOxit or similar is god to finish, but it does not cut the green stuff. You don't have to worry about all connections, but those between battery/R/R and fuse box are most important.

    Any voltage drop will reduce your charging by an equivalent amount. So 350mVolts will reduce charging from 14.5V down to 14.15V

    Quote Originally Posted by PeterBoomhut View Post
    When a short circuit this item the loading voltage is max 13,4 Volt, and that's to low.
    Not sure what this means, but it is probably not one of the prescribed tests as there are no short circuit tests. Do teh Quick Test and report the three numbers. I woudl do this after chemically cleaning corrosion and treating with something becuase the brass will re corrode fast.


    Sorry for the bad language , I'm Dutch and mu English is rusty.[/QUOTE]
    Read about Charging Quick Test GS Charging Health GS Stator

    "The smallest giant of mankind, is he who stands on the shoulders of a larger giant who himself stands on the shoulders of yet a larger giant, and therefore sees the most light from GOD." Posplayr 2017 adapted from : Bernard of Chartres


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    First of all, thanks for the response. Since the bike is with my son-in-law, I will come with the quick test values ​​tonight.
    When a short circuit this item the loading voltage (Battery) is max 13,4 Volt, and that's to low.
    By that I mean I made a connection from + Rectifier to + Battery, so parallel over the main fuse.

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    Quote Originally Posted by PeterBoomhut View Post
    First of all, thanks for the response. Since the bike is with my son-in-law, I will come with the quick test values ​​tonight.

    By that I mean I made a connection from + Rectifier to + Battery, so parallel over the main fuse.
    OK, and I understand why you might want to do that test but the result doesn't point to anything specific (i.e. actionable).

    If you want to measure voltage drops measure them directly without a short circuit trying to raise the voltage.

    If you had a bad stator, the voltage might not rise with RPM because the stator is at max output, but you still have voltage drops (dirty contacts). So shorting will not be able to determine anything.

    The Quick Test is to test and divine what is going on in order to direct follow-on testing.

    As a general rule, I would clean up connections and grounds early on because this is equivalent to driving a car without checking the air in the tires. The car might drive, but is something you are going to want to remedy at first opportunity.

    Given you have only 13.4V (assuming that was at 5K RPM), my guess is the stator is low, but not really knowing how you shorted the lines it could still just be connections.
    Read about Charging Quick Test GS Charging Health GS Stator

    "The smallest giant of mankind, is he who stands on the shoulders of a larger giant who himself stands on the shoulders of yet a larger giant, and therefore sees the most light from GOD." Posplayr 2017 adapted from : Bernard of Chartres


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    20200707_170744.jpg
    I'll clean the contacts. Wanted to see if shorting the main fuse gave better results.

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    Thanks for putting the extra effort into organizing your measurements. Without going through every measurement I will highlight a few things.

    I assume you mean stator leg (or Phase) when you label something as Generator. Common terminology is to describe the stator as 3-Phase and each wire coming from the stator is informally called "leg".
    If you want to call the stator a generator, I would not chide you, but it is technically an PM alternator.

    Your note says you are using a Shindengen R/R but there is no model number? Is it a 5 wire or 6 wire? Is it Shunt or Series?

    You should assume that anytime the key is on the headlamps should be on. The rest of the headlamp off measurements are redundant at best and can be misleading becuase they are at reduced load.

    ANALYSIS:


    1. When you see voltages drop from 2500 RPM to 5000 RPM this indicates that the extra current load is dropping a higher voltage between R/R and Battery. Plain and simple have dirty connections.
    2. Your "Voltage Drop" measurements also indicate 0.5V drop, but I don't know what RPM this was at. I suspect 1500 or 2500 RPM and they get bigger at 5000 RPM (my guess). Your "Short circuit main fuse" tests indicate a 0.87V improvement at 5000 RPM.
    3. The battery portion test comparing Step #1 and Step #2 should have been with lights on. If it was not, then with teh additional load the battery woudl probably drop another 0.5V. This indicates the State Of Charge(SOC) of the battery is low.
    4. Finally, you have concerns about the Leg-Ground tests at 5K RPM. This is not the first time that we have had similar results reported (leg-ground 30 VAC present but the bike seems to charge). If we use your ohm meter tests, you show an open with the VOM (probably 9VDC) potential. This is insufficient to break down the insulation. At 5K RPM your generator is producing 70 VAC (which is a little low) but is apparently enough to break down the insulation. When the stator is connected to an R/R which is connected to a battery, the voltage across the stator does not exceed about 20VAC zero to peak (you can only raise teh battery voltage so much). So it can be that the stator is simply not operating in the voltage regime being tested. I should clarify that a stator in good condition will still be isolated at 5K RPM, so the fact that there is voltage can still be taken as a forewarning of accumulation insulation breakdown (the stator is breaking down although still functioning).


    RECOMMENDATION:
    • Chemically clean all connections and fuse box between R/R and battery. (vinegar or Naval jelly cuts the green gook). Surface preparation after with DeOxit or similar protects the stripped bare surfaces.
    • Remeasure the voltage drops (without doing the shorting test).
    • Recharge the battery so it drops less than 1.0 volt with key on (set #2).
    • Redo the Quick Test till you get at least 14.25V at 5K RPM.


    Final note:

    The typical current running out of the R/R and returning through the grounds is 10-13 amps DC (depending on RPM)
    A 0.1 ohm resistance will drop 1V at 10 amps. To get the total voltage drops down to 100 mV your woudl need to lower the total resistance down to 0.01 ohms and each individual connector/crimp some fraction of that.
    This not any contact but rather those between R/R and Battery.

    This is why chemical cleaning and proper preparation to forestall the inevitable corrosion buildup is essential for peak charging.
    Read about Charging Quick Test GS Charging Health GS Stator

    "The smallest giant of mankind, is he who stands on the shoulders of a larger giant who himself stands on the shoulders of yet a larger giant, and therefore sees the most light from GOD." Posplayr 2017 adapted from : Bernard of Chartres


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