Question about 1984 Dodge D150

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I have a drag car and i've been running a 3 wire gm alternator (100amp) for 3 years with no problems. i took the red wire to a switch inside (not the battery wire) so i can turn the field off before i make a pass. the white wire was left alone. this has always worked. recently i was changing the belt and the threads for the bolt on the back was stripped. i took the alternator to the parts store and it was replaced. i reinstalled the new one in the same manner as the old one. now the alternator gets really hot and the belt starts squeeling. i took that alternator back and it was replaced. its still doing the same thing. i tested the voltage at the battery while the car running and it was only 12.3 volts. i took the alternator and had it tested and they said everything checked out. please help

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@ 12.3 v the alt is working at near, very near max output and will overheat and eventually fail. The lower the voltage, the higher the amps. You say it has always worked interupting the red wir. Interupting the red wire is the same as running the alternator without a load, which causes the unit to run wide open in voltsge. It may terminate the load but causes the unit to run wild or wide open on voltage output. Alternators are unlike a generators. Of course I sure you are aware that one is ac and the other is dc volts. Although parasitical, an alternator does not take much to charge, in fact it charges from the minute it starts tuning. If the battery and electril loads are minimize the alt. is virtually free wheeling. But to remove the load entirely will take it out. If you want it to stop charging, try interupting the exciter wire. It acts as a switch to turn the alt on and off by deenergizing a field coil. Good Luck, Ned

Posted on Sep 24, 2009

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I would say it maybe in your switch itself.possibilly you could have a power draw going on somewhere.such as a short.really about all it could be the 3 wire gm alt large red wire battery white wire is for the dummy light the small red wire is the turn on for alt.ALSO being the bolt was stripped and at hi rpm,s the alt maybe looeining causeing friction and over heating of alt by slipping of belt. may seem tight after words but mave have loosened just enought to only produce 12.3 volts.I have a 300 amp alt and 6 batterys in my car to produce amplifier power.your a drag racer im a DB DRAG RACER. In the car audio i do all own installations.its some wire?.lol

Posted on Sep 24, 2009

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You need to upgrade,to a 2000 amp or 2500 amp alternator to alimitate the over heating problem you are having.

Posted on Sep 24, 2009

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