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low voltage problems

Old Aug 28, 2011 | 08:24 PM
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Default low voltage problems

i have a 5.3 lmg that i swapped into a 69 nova and i am having a voltage issue. the motor will start up and run fine no problems but after a few minutes the motor would bog down and shut off. i performed the diagnostic and determined the alternator was bad so got it swapped out for a new one. shortly after this the motor ran fine but when i tested the voltage it showed only 12 volts and the motor still bogs but not as bad. i had the alternator tested and it passed so i am lost now and need help. the computer shows a generator L circuit dtc if that helps. i was thinking maybe the computer is limiting the voltage because currently i am only running a water pump and alternator and the computer no gauges, fans or any other things to draw power. i am unsure what is wrong.also i have no o2 sensors yet

thanks, robert

Last edited by 5.3Lnova; Aug 28, 2011 at 08:27 PM. Reason: misspelled word
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Old Aug 28, 2011 | 08:41 PM
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You need to put a light or resistor in the alternator circuit to make it charge..ie duplicate the warning light that is in dash on oem setups. Do searches on subject to find details on how to do it.
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Old Aug 28, 2011 | 08:53 PM
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Originally Posted by 5.3Lnova
i have a 5.3 lmg that i swapped into a 69 nova and i am having a voltage issue. the motor will start up and run fine no problems but after a few minutes the motor would bog down and shut off. i performed the diagnostic and determined the alternator was bad so got it swapped out for a new one. shortly after this the motor ran fine but when i tested the voltage it showed only 12 volts and the motor still bogs but not as bad. i had the alternator tested and it passed so i am lost now and need help. the computer shows a generator L circuit dtc if that helps. i was thinking maybe the computer is limiting the voltage because currently i am only running a water pump and alternator and the computer no gauges, fans or any other things to draw power. i am unsure what is wrong.also i have no o2 sensors yet

thanks, robert

Computer has nothing to do with the alternator as far control. The voltage regulator is inside the alternator. It will determine what it needs to put out in voltage and current as determined by the loads you put on its output. It sounds as if the guy above is right. You arent giving the alternator excitation so its basically just idling on its output. You should be getting around 13.8v or higher as measure at the battery while engine is idling.
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Old Aug 29, 2011 | 02:51 PM
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so did a search found the info but not all of it i am confused so please correct me if i am wrong. to my understanding i need a wire with a indicator light between the battery and the alternator? but i don't know which wire on the alternator and can i add the wire to ignition switch wire?
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Old Aug 29, 2011 | 07:25 PM
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Originally Posted by 5.3Lnova
so did a search found the info but not all of it i am confused so please correct me if i am wrong. to my understanding i need a wire with a indicator light between the battery and the alternator? but i don't know which wire on the alternator and can i add the wire to ignition switch wire?
Pick a lamp or a 500 ohm resistor. Either one will originate from a 12v "key on" source, go through your above "choice", and end at the "L" terminal on the alternator pigtail.
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