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Old 07-14-2000, 09:57 AM   #1

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What causes an alternator to fail?

What causes an alternator to fail?

Trying to draw more amps from your electrical system than the alt is designed for will eventually make the alternator fail. Is this correct? What exactly happens in this case?

I've also heard that disconnecting the positive battery terminal while the engine is running can cause a voltage surge that can damage the diodes in an alt. Is this true?

What else can cause an alternator (either the alt or internal voltage regulator) to go bad? (other than wearing out the brushes)
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Old 07-14-2000, 03:10 PM   #2

Join Date: Mar 2000
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If you overtax an alternator it fries. Gets too hot, stuff breaks or melts, diodes, regulators and such. Worst case is that your car will catch on fire, especially if wiring is too small or faulty.
Call an electrical auto shop or a place like Battery Masters. They can expand on my theory.
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Old 07-16-2000, 03:37 AM   #3

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Belker, unhooking the pos batt terminol is a deffinate no no, a guy i went to tech with did that on a cadalac and instantly caused 4000 dollars canadian damage to the vehicle heres what haappans
the voltage actually enters the batt through the pos terminal, the batt is 12 volts (ok 12.6 or so) in order to keep this charge and run the accesorys the alt must put out roughly 14.4 volts, the alt knows how much to put out because it sees the resistance that the batt has, now if you remove the pos terminal the alt sees an infinate resistance and trys to charge what is not there, the alt is capable of producing thousands and thousands of volts and when it has nothing to hold it back (batt, the voltage regulater only regulates upon what it sees for resistance, so no resistance means no regulater either) it does produce the thousands of volts, in an ideal case your fusable links will blow before any real damage but this is not always the case and in my buddys case at tech all the computers and sensors were imidiatly fried, this voltage can actually kill a human if he/she holds the terminal and a ground at the same time
sorry so long winded and im sure i didnt help you out any with your questions but i hope someone learned something
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