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Old 08-15-2010, 12:53 PM
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Alternator wiring is wrong

What's Happening Hot Rodders? I think my alternator is wired wrong. I have 2 thin wires thats coming from my alternator 1 is running to my msd 6 al box the other is running to my starter. From the starter is the positive wire that runs to the battery is there any problem with that.?

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Old 08-15-2010, 03:15 PM
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Where is the large output wire going from the alt?

Is this on a drag car or what?
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Old 08-15-2010, 04:01 PM
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No its ran 4rm the starter to the battery and no its not a drag car but i switched the motor to high performance 400 sbc
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Old 08-15-2010, 07:37 PM
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If you have a problem explain it. If you have a question be precise. What kind of car. Details help. Then maybe someone could provide an answer.

vicrod
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Old 08-16-2010, 07:20 AM
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More info is needed for sure. Which connection # goes where.
If one is connected to the msd, is that for switched power.
Is your alternator not working?
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Old 08-16-2010, 10:57 AM
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Quote:
Originally Posted by vicrod
If you have a problem explain it. If you have a question be precise. What kind of car. Details help. Then maybe someone could provide an answer.

vicrod
Even better would be what type of alternator is it? If it's a GM internally regulated 10SI, we also need to know if it's a factory three wire alternator or an aftermarket one wire alternator.
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Old 08-16-2010, 01:29 PM
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its a 86 monte carlo ss with a sbc 400 delphi alternator not to sure how much amps and its a 3 wire
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Old 08-16-2010, 03:24 PM
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Quote:
Originally Posted by McSS86
its a 86 monte carlo ss with a sbc 400 delphi alternator not to sure how much amps and its a 3 wire
Again, just to be clear, we're talking about a 10SI alternator and not a CS130, right?

Google "10SI wiring" and you find these:



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Old 08-18-2010, 12:13 PM
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Details are still sketchy but:

that 1st diagram showing the #2 wire going to the larger (+) battery terminal is not really correct. It works, but doesn't work properly. #2 is a voltage sense wire which should go as far away from the battery or alternator as possible. It tells the alternator to output more if the voltage drops at the rear lights (for example). It's so you get a good 12v everywhere, not just in the engine compartment.

#1 wire is just an idiot light, doesn't do much at all for the alternator function

#1 should only go to a dashboard light, not the msd

#2 could (thin wire) go to the (+) supply on the msd so long as the (+) on the msd also goes to the battery or fusebox positive supply. #2 does not supply power

the large 1/4" bolt on the alternator is the output....goes to battery
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Old 08-18-2010, 02:57 PM
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Quote:
Originally Posted by bubbahotep
Details are still sketchy but:

that 1st diagram showing the #2 wire going to the larger (+) battery terminal is not really correct. It works, but doesn't work properly. #2 is a voltage sense wire which should go as far away from the battery or alternator as possible. It tells the alternator to output more if the voltage drops at the rear lights (for example). It's so you get a good 12v everywhere, not just in the engine compartment.

#1 wire is just an idiot light, doesn't do much at all for the alternator function

#1 should only go to a dashboard light, not the msd

#2 could (thin wire) go to the (+) supply on the msd so long as the (+) on the msd also goes to the battery or fusebox positive supply. #2 does not supply power

the large 1/4" bolt on the alternator is the output....goes to battery
Sorry, but you're wrong on several points here. First, the #1 wire is not "just an idiot light". It is the activation wire for the 10SI. The other side of the indicator bulb sees constant +12V, and this activation wire needs to see that voltage through the resistance of the bulb (or an inline resistor of about 35 ohms) to properly turn on the alternator at idle. That's why one wire versions don't charge at idle.

Second, the #2 wire is the voltage sensing wire, as you've correctly pointed out. It is used as a feedback loop by the regulator. You are correct that you should really run that wire all the way to the junction block to get a proper reading on voltage drop, but the alternator will work and will charge with the #2 wire simply attached to the BATT stud on the alternator. You should NOT use the #2 wire to supply voltage to the MSD.

Edit: Sorry, I just reread your statement on the #2 wire and I do agree with what you said.
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Old 08-18-2010, 06:31 PM
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Quote:
Originally Posted by joe_padavano
Sorry, but you're wrong on several points here. First, the #1 wire is not "just an idiot light". It is the activation wire for the 10SI. The other side of the indicator bulb sees constant +12V, and this activation wire needs to see that voltage through the resistance of the bulb (or an inline resistor of about 35 ohms) to properly turn on the alternator at idle. That's why one wire versions don't charge at idle.

Second, the #2 wire is the voltage sensing wire, as you've correctly pointed out. It is used as a feedback loop by the regulator. You are correct that you should really run that wire all the way to the junction block to get a proper reading on voltage drop, but the alternator will work and will charge with the #2 wire simply attached to the BATT stud on the alternator. You should NOT use the #2 wire to supply voltage to the MSD.

Edit: Sorry, I just reread your statement on the #2 wire and I do agree with what you said.

My bad, forgot about the #1 also turning it on. So to the guy that posted originally, and seems to have vanished, joe is 100% right

I think we are in agreement with the #2 however. I wasnt saying to use it to POWER the MSD. But, it can go to the 12v line that feeds the msd which is usually a short run from the alternator #2 to the MSD supply wire. Im assuming the MSD gets power from the ignition and the #2 will therefore be seeing that "long" run through the ignition key. Does that make sense?

+12v from ignition---------MSD thin red wire from ignition key
|
#2----------------------

Again I say "can go", not SHOULD go. Ideally it would go way back to the *** end of the vehicle.
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