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Alternator wiring ( 3 wire)

Alternator wiring ( 3 wire)

Old November 18th, 2018, 05:55 AM
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Alternator wiring ( 3 wire)

Hi guys,
Certain this has been addressed before but just cant find it. Working on my son's rat rod with every varied part that could work used to repair by previous owners. As I know alternators from my Oldses, Large red wire to positive stud on back of the alternator, and a two wire pigtail into the #1 and #2 male tabs on the outer edge. Here's the concern!! Rather than a stock pigtail, it was replaced with two black wires and crimp ends to attach. My son did not note which wire went to 1 or 2. Please educate me as to #1 and #2.

Thanks,
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Old November 18th, 2018, 06:19 AM
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#2 will be hot at all times. #1 will be hot with key on only. #2 is battery sense wire. #1 is Ign activated to excite alternator to charge and it goes through an indicator light or a resistor wire.
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Old November 18th, 2018, 06:48 AM
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Stellar,
I knew that #2 should be hot. Presently the only wire hot at all times is the larger red wire to Bat. Neither of the 1 or 2 wires is live as well. Hmmm. I've seen diagrams showing a jumper from the large bat. wire to number 2. Please further educate the route of #1 as this chevy truck has been highly tampered with.

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Old November 18th, 2018, 07:00 AM
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Let's start with a more basic question. Is this an internal or external regulator system?
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Old November 18th, 2018, 07:12 AM
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Joe,
Internal to my knowledge
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Old November 18th, 2018, 09:10 AM
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Originally Posted by 70 ctls View Post
Joe,
Internal to my knowledge
If it's a 10SI/12SI, then the wiring is easy. Here is the terminal orientation. Most of the cases actually have raised numbers cast into them.



The #1 terminal is the exciter and goes to the GEN light on the dash. This terminal needs to be connected to a switched 12V source with an inline resistor of about 35 ohms for the alternator to charge properly. The filament in the idiot light bulb provides that resistance. If you don't have a light, use an inline resistor to connect this to a 12V source that is only powered in RUN.

The #2 terminal is the sense terminal and should be routed to whatever main terminal block you are using. You can route it to the BATT terminal on the back of the alternator for simplicity, but that pretty much defeats the purpose as you won't be properly sensing any voltage drops in the system. The sense wire measures actual system voltage at the point where it is connected and adjusts regulator output accordingly.

Of course, the BATT terminal just goes to the battery or terminal block.
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Old November 18th, 2018, 10:30 AM
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Joe,
Thank you for the education and direction in how to proceed. As my grand kids say............ " You're the Man "
John
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Old November 19th, 2018, 05:36 AM
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Joe,
In keeping with the 'rat rod backyard repaired' concept of this truck, could I run the exciter wire from a RUN source through a Mopar ignition ballast mounted on the firewall only because I have a few on the shelf?

John


Don't think I've converted. I am an OLDS man ! This is my son's newest project. It's helped me clean out my garage as I have installed many Olds parts in this 'rat':
'69 Cutlass S Steering Wheel
'49 clock ( 12 v to 6 v in-line converter installed to operate properly )
'36 dual ram head horns ( wired directly to 12 v.) They roar !!
'48 hood ornament. ( outfitted with internal light to provide 'glow' of the Lucite wings of the Rocket.)
'69 4 barrel air cleaner housing

I'm certain He'll come up with an idea and I'll have the solution from my surplus of Olds parts. I told him if he sells it I want time to take some more valued parts back.

John
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