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  1. #1
    RumRunnerRon's Avatar
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    Great thread if you think you are having rectifier or stator problems.

    Great info , great pics . Shows what to look for and discusses how to go about doing the job in detail. Possibly deserving of being a sticky IMO.

    http://www.greenhulk.net/forums/showthread.php?104284-Check-out-these-pics-of-my-old-rectifier!&highlight=Rectifier


  2. #2
    I hate to disagree with you Ron, because you post excellent stuff, but I take issue to this thread. There are two main things I think are wrong with it. One is that it doesn't give you any tips on diagnosing rectifier/regulator issues. The second point is about the conclusion that the stator in the pictures was toast.

    I agree that the stator in the pictures had been overheated, but I don't think it had been overheated to the point that it was no good.

  3. #3
    RumRunnerRon's Avatar
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    Quote Originally Posted by Sea Dood View Post
    I hate to disagree with you Ron, because you post excellent stuff, but I take issue to this thread. There are two main things I think are wrong with it. One is that it doesn't give you any tips on diagnosing rectifier/regulator issues. The second point is about the conclusion that the stator in the pictures was toast.

    I agree that the stator in the pictures had been overheated, but I don't think it had been overheated to the point that it was no good.


    It's cool Dood, difference in opinions is what makes the world go round. While the thread does not take the time to tell you how to specifically diagnose the rectifier it's clear the OP had moved past the need for that by his very clear pics of where the board was burnt. Not saying that will be the case every time but in the OP's case it was. The pics of the stator to me are equally as helpful in that they clearly show burnt fused metal on the ends in several places as well as overheated insulation. It even shows one common reason for the stator to short (metal shavings). IMO one of the best things it says right after the OP's first post is STOP. Before you test out that new rectifier you just put in why don't you do this. So many seem willing to roll the dice on that one. It also states why a visual inspection just might be the preferred method for checking the stator. This was advice given by someone with a good rep on the forum. This saved the OP the cost of having to buy a second rectifier. It's a great example of what you could see.

  4. #4
    I am sensitive to issues regarding the charging system, mainly because I used to work for an alternator and starter manufacturer, and spent many a day helping diagnose alternator overheating issues. (I once spent a few interesting hours at the city bus maintenance depot in Shanghai after midnight trying to figure out why they were blowing alternators, but I digress...)

    In the thread you posted, I believe that the stator was fine. It was overheated because the rectifier shorted, but it was not overheated to the point of losing the integrity of the insulation. If he put on a new rectifier, it would not have been damaged.

    The only time that a new rectifier can be damaged by a bad stator is if there is a short to ground in the windings. This is easily checked with a DMM on any of the three yellow wires to ground. The reason this is so is because this system is a three phase full wave bridge rectification scheme, if there is a short in one of the windings, the other windings will try to output full power thru one of the diodes in the rectifier, overheating it. Interwinding shorts will not kill rectifiers, but will further overheat the stator windings.

  5. #5
    96XPSS's Avatar
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    The integrity of the windings can also be confirmed with a mega-ohm meter, which nobody has. I don't really see how you can make the assumption that the motor windings are ok, visually, because they didn't get "too hot." And if memory serves me correctly, he had already burned up one rectifier previously, before the one in the thread was pictured. This would also confirm the stator was shorted, obviously.

    But your "visual" diagnosis? Hmm...you are good if you can see under the outer windings. Do you have x-ray vision?

  6. #6
    You don't need a megaohm meter for diagnosing these windings, and it is not an encompassing test anyway. There are three failure modes on these stators, opens, shorts to ground, and inter-winding shorts. A megaohm meter will only tell you resistance to ground, which is pretty much useless test, because these are extremely low voltage windings. You could have a resistance to ground of a couple kilohms and it still would work fine.

    You would check the inductance of the windings to tell if you had a interwinding short. You don't really need to do this, as you can do a visual inspection to tell if one winding was more discolored that the others. Another instrument is a milliohm meter. I happen to have both of these, but I wouldn't really bother to use them.

    So all you really need is a decent DMM. Measure continuity for any opens. Measure resistance to ground, should be infinity on your meter.

    As I said in my post, I have a wealth of experience in determining failure modes in windings, and those windings look a bit overheated, but evenly overheated, and as long as there is no opens of shorts to ground, they should be fine. Also, the rectifier failed because one or more of the components in that assembly failed. THis is what overheated the stator. The stator did not cause the rectifier to fail.

    Quote Originally Posted by 96XPSS View Post
    The integrity of the windings can also be confirmed with a mega-ohm meter, which nobody has. I don't really see how you can make the assumption that the motor windings are ok, visually, because they didn't get "too hot." And if memory serves me correctly, he had already burned up one rectifier previously, before the one in the thread was pictured. This would also confirm the stator was shorted, obviously.

    But your "visual" diagnosis? Hmm...you are good if you can see under the outer windings. Do you have x-ray vision?

  7. #7
    96XPSS's Avatar
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    A DMM will not find a short under load. It will ohm fine, then when placed under a load, it is shorted. A Megaohm meter will. I use one daily to accurately determine motor failures where a standard DMM will not work. So...we will agree to disagree. Your wealth of experience does not work, or even validate, the experience in my world.

    This is a typical "engineer knows all and everyone else is ignorant" thread. Enjoy your opinion Dood. You've earned it, and we can read why you think so.

  8. #8
    Richieb's Avatar
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    Meg-ohm meter we use for insulation testing.

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