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Old 12-31-2024, 10:20 AM   #26
Kalums
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Re: Wiring in a larger alternator

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Originally Posted by Rich69shortfleet View Post
A 10si is a one wire alternator with an internal regulator.
Well apparently I have 2 voltage regulators, but this one is set up as a 3 wire and not a 1 wire + ground... Hhhmmmm... I've also done the AC/DC (great band) test this morning and.... *ding, ding ding* we have a winner!!! It is producing AC voltage and DC voltage...so a new Alternator should fix my problem in the end... I'm going to see later if Napa is open and Just nab a standard/ New 60(ish) amp, 10si. We will see if that fixes the issue. Again thank all of you for the help.

Follow up... I just learned the difference between a 10si and a 10dn...i have a 10dn with a 3 wire hook up... So there is that. Doesn't change the fact it is putting out AC and DC voltage indicating a bad diode(s).

Learned more... My alternator has connections on the top (10si) and not the back (10dn) so further digging is needed on my part to see of someone else did or half did a conversation *shrugs*

Last edited by Kalums; 12-31-2024 at 11:17 AM. Reason: Learned more...
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Old 12-31-2024, 01:06 PM   #27
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Re: Wiring in a larger alternator

There are a couple of really easy checks you can do, called out in the factory service manual (available free on this forum) One is using the grounding tab provided in the back of the 10-SI to eliminate the voltage regulator after you have your test meter hooked up correctly. The diode check is called out in the manual with nice pretty little pictures too. It shows you exactly where to put the leads of the meter.
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Old 12-31-2024, 01:26 PM   #28
Kalums
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Re: Wiring in a larger alternator

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Originally Posted by Orange Crate View Post
There are a couple of really easy checks you can do, called out in the factory service manual (available free on this forum) One is using the grounding tab provided in the back of the 10-SI to eliminate the voltage regulator after you have your test meter hooked up correctly. The diode check is called out in the manual with nice pretty little pictures too. It shows you exactly where to put the leads of the meter.
Sweet, thank you. Found it! I will do my voltage (etc) checks again.
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Old 01-01-2025, 12:45 AM   #29
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Re: Wiring in a larger alternator

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Learned more... My alternator has connections on the top (10si) and not the back (10dn) so further digging is needed on my part to see of someone else did or half did a conversation *shrugs*
Some aftermarket 10dn alternators have the plug on top instead of the back such as those made by Tuff Stuff. The question is, does it use a plug that has prongs like "| |" or "- -" The vertical ones are 10dn, the horizontal ones are 10si.
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Old 01-01-2025, 01:06 AM   #30
Kalums
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Re: Wiring in a larger alternator

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Originally Posted by Rich69shortfleet View Post
Some aftermarket 10dn alternators have the plug on top instead of the back such as those made by Tuff Stuff. The question is, does it use a plug that has prongs like "| |" or "- -" The vertical ones are 10dn, the horizontal ones are 10si.
It looks older, but they are vertical (10dn). So after testing per the service manual... I'm still getting an output of AC and DC voltage up to the regulator on the radiator support... But testing the "output" from the regulator to the rest truck is DC... BUT there is a significant voltage and amperage drop from the regulator at idle. It picks up to normal when truck is revved to 1200+ rpm on the engine... *shrugs* at this point I'm tempted to replace the alternator with a 10si or 12si and do the conversion/new wiring. I think that will benefit me most in the long run.
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Old 01-01-2025, 12:15 PM   #31
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Re: Wiring in a larger alternator

So... Found something else interesting while poking around in/with the wires from my alternator to the battery is "solid" (think house wire/ Romex) not sure if that has anything to do with anything... But this just keeps getting stranger as I go along.
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Old 01-01-2025, 12:30 PM   #32
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Re: Wiring in a larger alternator

Now we've got to see pictures...
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Old 01-01-2025, 12:34 PM   #33
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Re: Wiring in a larger alternator

>>I'm still getting an output of AC and DC voltage up to the regulator<<

How much AC are you actually getting ?
Unless you actually know what is going on, don't over think this AC idea.

The first image shows the 3-phase voltage as produced in the stator windings. The diodes chop off the Negative side and you end up with a 12 volt ripple as displayed in (A) in the second image. The wire resistance and the battery itself will filter and smooth out that ripple and your meter will see a 12 volt DC voltage.

Another thing to consider is the relay voltage regulation provided by the mechanical voltage regulator. The relay contacts in the upper-right side of the relay image can only supply the Field windings with 0 volts or 12 volts. The upper contact is Ground and the lower contact is 12 V. The center contact is rapidly fluctuation up and down, constantly turning the Field winding ON/OFF. This could actually be seen as a AC signal, but at a much higher frequency than the 3-phase signal.

Don't expect the 10DN output to be ripple free. The battery doesn't care, neither should you.
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Old 01-01-2025, 01:01 PM   #34
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Re: Wiring in a larger alternator

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Now we've got to see pictures...
Wish granted, the "coil" is what I pulled out of the truck... It went from the driver's side of the engine to the fender well and around the front over the radiator and then there was some coiled up under/behind the battery tray (or what is left of it). The second is outside next to the truck, I bent the tip back out/around, still has dielectric grease on it... Lighting in my garage is terrible. P sry for the garbage pictures.
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Old 01-01-2025, 01:07 PM   #35
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Re: Wiring in a larger alternator

Interesting. I don't know what kind of wire that is. The insulation looks kind of too thick for romex.
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Old 01-01-2025, 01:07 PM   #36
Kalums
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Re: Wiring in a larger alternator

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Originally Posted by RichardJ View Post
>>I'm still getting an output of AC and DC voltage up to the regulator<<

How much AC are you actually getting ?
Unless you actually know what is going on, don't over think this AC idea.

The first image shows the 3-phase voltage as produced in the stator windings. The diodes chop off the Negative side and you end up with a 12 volt ripple as displayed in (A) in the second image. The wire resistance and the battery itself will filter and smooth out that ripple and your meter will see a 12 volt DC voltage.

Another thing to consider is the relay voltage regulation provided by the mechanical voltage regulator. The relay contacts in the upper-right side of the relay image can only supply the Field windings with 0 volts or 12 volts. The upper contact is Ground and the lower contact is 12 V. The center contact is rapidly fluctuation up and down, constantly turning the Field winding ON/OFF. This could actually be seen as a AC signal, but at a much higher frequency than the 3-phase signal.

Don't expect the 10DN output to be ripple free. The battery doesn't care, neither should you.
I learned something new today, I didn't realize/know any of that... My AC voltage fluctuates the most widely with engine rpms however there was a 2-5 volt and 0.5 amp (generally) fluctuation at idle... Again I think I'm just going to convert to a 12si and rewire... I'm already partially there ripping up/out some of the harness...
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Old 01-01-2025, 01:10 PM   #37
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Re: Wiring in a larger alternator

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Interesting. I don't know what kind of wire that is. The insulation looks kind of too thick for romex.
It says "drct bry 12" on it.... So I'm thinking it is direct bury 12ga THHN. *shrugs* IDK I'm not any type of electrician. (well maybe "shade tree" *laughs*)
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Old 01-01-2025, 01:43 PM   #38
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Re: Wiring in a larger alternator

I swapped a 10SI into my K20 close to 10 years ago and never looked back. I had a couple new external regulators that crapped out on me in short order so I upgraded. I’ve never had a problem with charging or anything like that, but electrically my truck is mostly stock. The wiring changes to go from a DN to a 10/12SI are really really small and simple. I’d bet someone hooked up the plug at the alternator backward at some point or another on yours, if that happens it will cause the alternator to go to full output and burn that wire over the radiator up. I’ve seen it a few times on these trucks.
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Old 01-01-2025, 01:53 PM   #39
Kalums
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Re: Wiring in a larger alternator

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I swapped a 10SI into my K20 close to 10 years ago and never looked back. I had a couple new external regulators that crapped out on me in short order so I upgraded. I’ve never had a problem with charging or anything like that, but electrically my truck is mostly stock. The wiring changes to go from a DN to a 10/12SI are really really small and simple. I’d bet someone hooked up the plug at the alternator backward at some point or another on yours, if that happens it will cause the alternator to go to full output and burn that wire over the radiator up. I’ve seen it a few times on these trucks.
Not gonna lie I've given up on this endeavor I ordered a 12si (94 amp) and "conversion kit" and I'm currently wrapping my 6-8-10ga wires together with wireloom and cloth(factory style) electrical tape, to replace the wiring going across the radiator support.
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