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Bad alternator update

M

mkirsch

Well-known Member
Last week I had a suspected bad alternator on a W-400 12V conversion.

Took the alternator back to the auto parts store. They put it on their testing machine. A few seconds after it started spinning the alternator, there was a POP, and the testing machine went dead.

The alternator was so bad, it BLEW UP the testing machine!

First time I've ever seen an alternator/generator test fail.

Anyway, bad alternator confirmed. New alternator works GREAT!
 
An unregulated Alt can and will make hundreds of volts. That is my rationalle for fuse links that I put in the system. Better a fuse link than the syste,.
 
Yep and that is the reason I say never pull a battery cable to see if the alternator is working since when you do that the VR sees a dead battery and puts out max amps and volts and in turn fries the regulator so then it is putting out 90 plus volts and if you get between the cable and ground you can in turn be fried
 
I don't know the cause of the alternator test stand going POP but I will say this. More than one time, when the stator windings were shorted out in an alternator, you would be amazed about how much power it took to turn that in the test stand. It would stall our machine right out and I tested many 100 amp alternators at full 100 amp output at recommended 13 volts test. It made the stand work hard but not nearly as hard as the bad alternator which was not even coming close to heavy output. Ones that tested way high on voltage didn't require much power to turn as long as you wern't loading it down with heavy amperage at the same time.
 
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