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Thread: alternator

  1. #1
    'LS' Member
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    alternator

    Is there a way to check and see how bad my alternator was to my new one? Problem is i've taken it out so can i put a multimeter on the positive the other probe onto the chassis to get a reading? Or does it have to be in the car. I've got a new alternator because i put my battery on the wrong way round and my alternator started smoking :-S

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    'GLS' Member
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    As you have the alternator off of the car, your best bet would be to strip it down, noting the location of the mounting.
    The most likely part to have suffered due to polarity reversal, is the diode pack. If you separate this from the stator windings, you can use your multi-meter to check the diodes (which are most likely cooked) If you are fortunate, and they are OK, when you use the diode tester or the ohm meter settings, you SHOULD only get a current flow in one direction through the diodes, if you get a reading in BOTH directions, you need a new diode pack. BUT before you go out and buy one, check the stator windings are not burned (This could be where the smoke was coming from) - These windings are varnish coated, if it looks burned, then it is and it probably won't be economical to repair it - You really need a Megger type insulation tester to check this.
    It is also possible that the voltage regulator suffered from the polarity reversal, the best way to check that is by substitution, or you could simply re-assemble the machine and try it - if it still doesn't work, the likely culprit would be the regulator.

    Regards.

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