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1986 K30 - Rapid Learning

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mrk5

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Those 10/12SI alternators aren't wired that way. It needs power on both of the terminals in the small plug, BUT one has to have less voltage than the other ( battery voltage). I know that sometimes just the bulb in the charge light makes enough resistance to make it charge, but I may be remembering it incorrectly.
I think you might have that backwards. I think the CS alternators need the resistance wire or bulb. I have a 12si alternator.
 

6872xtc

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I think you might have that backwards. I think the CS alternators need the resistance wire or bulb. I have a 12si alternator.
I am fairly confident in my information on that. As @imiceman44 said, the CS series has remote sensing, not all factory installations used it, but they were capable of it.
 

mrk5

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Those 10/12SI alternators aren't wired that way. It needs power on both of the terminals in the small plug, BUT one has to have less voltage than the other ( battery voltage). I know that sometimes just the bulb in the charge light makes enough resistance to make it charge, but I may be remembering it incorrectly.
After doing some looking I was wrong. You do need to have #1 terminal connected to a switched 12V source. If you don't have the idiot light, you may need a diode on that wire to keep it from back feeding the ignition and keeping the vehicle running.

Apparently you don't technically have to have the #2 wire connected. On the SI alternators, the remote voltage sensing is optional. Without it, the alternator uses the charging post to sense voltage.

I was reading all this here: https://alternatorparts.com/faq.html
 

Wes Harden

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Good info.
@shima needs to check the bigger wire in the 2 wire plug for voltage with key off then on. No voltage off, and should see battery voltage with key on.
 

imiceman44

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After doing some looking I was wrong. You do need to have #1 terminal connected to a switched 12V source. If you don't have the idiot light, you may need a diode on that wire to keep it from back feeding the ignition and keeping the vehicle running.

Apparently you don't technically have to have the #2 wire connected. On the SI alternators, the remote voltage sensing is optional. Without it, the alternator uses the charging post to sense voltage.

I was reading all this here: https://alternatorparts.com/faq.html
And I have seen plenty of SI alternators setup with one wire on that plug.
At first it puzzled me then I learned more about that
 

mrk5

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And I have seen plenty of SI alternators setup with one wire on that plug.
At first it puzzled me then I learned more about that
I still think in a scenario like mine with a bunch of loads that aren't part of the factory harness as well as the non-factory charging wire , it's a good idea to run the #2 pin to the battery and/or where the added loads are connected.
 

Wes Harden

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Hmm I am not understanding, #2 pin in small plug goes to voltmeter or charge light, no ?
The #1 pin in plug is from ignition switch power.
 

shima

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Thanks for the responses guys! I have some reading to do before I can fully understand your comments and suggestions... I'm going to start with the FAQ link that @mrk5 posted earlier.

Last night, I finished installing the new battery cable. The pigtail is just disconnected right now... I wrapped the exposed end in electrical tape.

The truck's starter sounded great when I fired it up, so that's awesome. Unfortunately my voltage reading with the truck running was just below 12V. I had the headlights on when it was running. I also blipped the throttle a few times and tapped the alternator with a hammer.

So next steps for me are to do some reading on that FAQ page and then revisit your guys' responses / comments.

I also picked up some things from Harbor Freight in case I need to do any work on the electrical stuff. I call this the, "I have no idea what I'm doing and hope this is a good start" package:

PXL_20220513_015517663.jpg
 

Wes Harden

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good start, what diameter is solder ? lead free ? do your self a favor and get some Klein crimpers, Lowes has them for reasonable $.

I have these 2



The blue handle are adequate.

You will see the difference, if you get any time on the HF crimping tool.

going to need some 10ga connectors (yellow)

I still think you have a blown fuse link, but I'm sure you'll figure it out.
 

centexk5

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I’ve got ratcheting crimpers for insulated and non insulated terminals that are awesome.
 

Wes Harden

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I have those too, but most people won't spend the money for them. A set of 3 from Packard Electric. The 2 I linked I keep in my travel kit.
 
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