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Alternator Wiring Issue...need help

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Old Feb 28, 2013 | 12:15 PM
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Default Alternator Wiring Issue...need help
Have a 79 elco with 2004 5.3 Silverado Vortec. I have already replaced one alternator, and rewired to what I THOUGHT migh be correct. However, battery needs charging consistantly, and car dies immediately if positive is disconnected.

Trying not to have to do this again, I have a come to the trusted experts once again. Back of alternator wired to starter. On the plug top HOT wire to battery (S on alternator), and taped wire (I on alternator) hides a 470 Ohm 1/2 watt resistor wired to idiot light. L and P on alternator inactive. Although I have looked at numerous diagrams, have I wired incorrectly? And If so and I fix it, will alternator work or have I shot this one too? Same thing...will I need to replace resistor?

Thanks in advance for any help.
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Old Feb 28, 2013 | 12:31 PM
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Originally Posted by GoTTi-RR
Have a 79 elco with 2004 5.3 Silverado Vortec. I have already replaced one alternator, and rewired to what I THOUGHT migh be correct. However, battery needs charging consistantly, and car dies immediately if positive is disconnected.

Trying not to have to do this again, I have a come to the trusted experts once again. Back of alternator wired to starter. On the plug top HOT wire to battery (S on alternator), and taped wire (I on alternator) hides a 470 Ohm 1/2 watt resistor wired to idiot light. L and P on alternator inactive. Although I have looked at numerous diagrams, have I wired incorrectly? And If so and I fix it, will alternator work or have I shot this one too? Same thing...will I need to replace resistor?

Thanks in advance for any help.
You only need the resistor if you are not using a light to excite the alternator. If you are using a light and a resistor then you are most likely not even exciting the alternator.
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Old Feb 28, 2013 | 12:49 PM
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Originally Posted by GoTTi-RR
Have a 79 elco with 2004 5.3 Silverado Vortec. I have already replaced one alternator, and rewired to what I THOUGHT migh be correct. However, battery needs charging consistantly, and car dies immediately if positive is disconnected.

Trying not to have to do this again, I have a come to the trusted experts once again. Back of alternator wired to starter. On the plug top HOT wire to battery (S on alternator), and taped wire (I on alternator) hides a 470 Ohm 1/2 watt resistor wired to idiot light. L and P on alternator inactive. Although I have looked at numerous diagrams, have I wired incorrectly? And If so and I fix it, will alternator work or have I shot this one too? Same thing...will I need to replace resistor?

Thanks in advance for any help.
Is it safe to assume the 'HOT WIRE' you are referring to is the one going back to position C2 (Red) 15 on the PCM? This is not wired directly to 12 volts. It goes through the PCM. Just confirming.

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Old Feb 28, 2013 | 01:15 PM
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Sorry for not explaining earlier....this is a carbed unit. There is no pcm on this car. Also, I took the resistor out, and while car is idling, still read 12.2 volts across battery. Not sure if resistor could have damaged alternator, or if I have something else wrong.
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Old Feb 28, 2013 | 01:48 PM
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Originally Posted by GoTTi-RR
Sorry for not explaining earlier....this is a carbed unit. There is no pcm on this car. Also, I took the resistor out, and while car is idling, still read 12.2 volts across battery. Not sure if resistor could have damaged alternator, or if I have something else wrong.
To test, use the resistor inline on the alternator 4 way metripack connector to an ignition power source. Dont use the bulb. If the bulb has too much resistance it wont excite the alternator. If it has too little resistance it can or could have damaged the alternator.

The only time a resistor is used is on a carbed setup or a 1998 and older lsx/ltx stand alone setup.
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Old Feb 28, 2013 | 10:03 PM
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got it figured out...the exciter was wrong...had to go to "L", then put in resistor, and wired to wiper circuit...idiot circuit was dead...imagine that. thanks all for the help!
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Old Feb 28, 2013 | 11:25 PM
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Originally Posted by GoTTi-RR
got it figured out...the exciter was wrong...had to go to "L", then put in resistor, and wired to wiper circuit...idiot circuit was dead...imagine that. thanks all for the help!
Awesome! I just assumed that you had it in cavity B for the L terminal. Its always the simple things!
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