Which Internally Regulated Alternator Should I Get?

[NorCalC20LWB]

Hey all, I know this is a question that has been discussed many times, but I'm having a hard time figuring out exactly which alternator to get to convert to internally regulated. I just got an AAW Classic Update wiring harness and need to get an alternator to with it, which must be internally regulated. I won't be running electric fans, big amps, etc. so don't think I need any massive amp output. Can somebody give me a part number to search for? So far all I've been able to figure out is 10 or 12SI. I'm sure this is listed somewhere in the search function, but filtering through all the posts has left me a bit confused.

[Willys_MB]

It depends on what accessories you plan on running. I had a 100 amp alternator from Summit that crapped out one week after the warranty ran out. Then I bought this one (for far less, too) and have been very happy with it. It was $10 cheaper when I bought it, though

ACDelco 335-1094 Professional Alternator https://www.amazon.com/dp/B007QBRAMM..._leB1sr7oLaxLI

[toolboxchev]

Check Mad Electricals website, believe they give some part numbers for a Buick application on a 12si

Will mount into a stock location on Gen1 SBC.

[NorCalC20LWB]

Thanks Willys, that looks perfect! I really like Shingle Springs BTW, nice area.

ToolBox, I will check out that website for what they suggest. Quick question, what is the difference between a 10SI and a 12Si?

[toolboxchev]

Originally Posted by NorCalC20LWB

Thanks Willys, that looks perfect! I really like Shingle Springs BTW, nice area.

ToolBox, I will check out that website for what they suggest. Quick question, what is the difference between a 10SI and a 12Si?

I dunno??? both are internally regulated though. Watch your amperage draw on your system, Some stock type stuff has its limitations, it also depends on how you wire it also.

How a vehicle is wired and what the actual draw of components is, I am learning, is very important.

[Stocker]

I went through a similar situation a couple years ago, got lots of great help & advice here. The one I got did the trick and I'm very pleased with it. It's a 94A alternator for an '85 Buick Riviera, O'Reilly's p/n ULT R111785A.

https://www.oreillyauto.com/detail/b...ternator&pos=4


Differences between 10SI and 12SDI are explained here: http://www.madelectrical.com/electri...elcoremy.shtml

[rpmerf]

The one on my truck is a 12SI, ~78 Amps, 9:00 clock. Think I ordered it for a 85 Rivera 305. I could had easily gone for the 94 amp, but I figured the 78 was closer to the stock 63 amp.

[Willys_MB]

Originally Posted by NorCalC20LWB

Thanks Willys, that looks perfect! I really like Shingle Springs BTW, nice area.

ToolBox, I will check out that website for what they suggest. Quick question, what is the difference between a 10SI and a 12Si?

Wow, I didn't realize you were here in Fair Oaks! Hi neighbor!

Here's a good article on it:

http://www.madelectrical.com/electri...elcoremy.shtml

I think the biggest difference between 10SI vs 12SI is how they're regulated. I believe the 10SI uses something called a one wire method, which is an older way of wiring the internal regulator, where the 12 SI uses the three wire method. Or maybe I have those reversed... I think the 12SI stays cooler and the three wire method helps keep the heat down. Here's an article on three wire vs one wire methods.

To sum it up, though: "The 1-wire alternator only has a sense of what it is sending current to, which is the battery. If the battery is up, it does not recognize a voltage drop. The three wire alternator senses voltage at the fuse block and the ignition, and the alternator will then charge more to get all the systems up to power."

https://www.rodauthority.com/tech-st...d-ron-francis/

[NorCalC20LWB]

Willys, that looks like a good deal, but not available until the end of April.

Stocker, the one you posted from Oreillys is a little more, but available today. Looks like there is a core charge, so assume I need to take them the old alternator if I go that route.

[Willys_MB]

Originally Posted by NorCalC20LWB

Willys, that looks like a good deal, but not available until the end of April.

Stocker, the one you posted from Oreillys is a little more, but available today. Looks like there is a core charge, so assume I need to take them the old alternator if I go that route.

Oh wow, I didn't even notice. Either way, what you're looking for is probably a 12SI alternator. Amazon may not be the best place to get it anymore because they're giving priority shipping to household goods. I tried to order some rust treatment and it would take over a month to get here, so I went to O'Reilly and got it for $5 more than I would have paid on Amazon.

[Stocker]

Originally Posted by NorCalC20LWB

Stocker, the one you posted from Oreillys is a little more, but available today. Looks like there is a core charge, so assume I need to take them the old alternator if I go that route.

Yessir, I paid a $15 core charge which they refunded when I took the old one in.

Side note: it doesn't need to be the same type, all they want is your old alternator.

[NorCalC20LWB]

Originally Posted by Stocker

Yessir, I paid a $15 core charge which they refunded when I took the old one in.

Side note: it doesn't need to be the same type, all they want is your old alternator.

Looks like the best option is the O'reilly alt. Thanks for all the suggestions guys, great info.

Stocker, are you going to the car show/parade in Weaverville on 7/4 I think?

[Stocker]

Originally Posted by NorCalC20LWB

Stocker, are you going to the car show/parade in Weaverville on 7/4 I think?

It depends..... on the virus (hopefully not a problem by then, but who knows) and on the heat. Many years it's just too dang hot for us to leave the house.

That's for the parade. The car show is usually the third weekend in August. Assuming they put it on this year....

[PepperTreeGarage]

I'm considering this one:

https://www.qualitypowerauto.com/ite...-regulator.htm

[Stocker]

Originally Posted by PepperTreeGarage

I'm considering this one:

https://www.qualitypowerauto.com/ite...-regulator.htm

That says it's a 1-wire, and some guys are fine with that. I personally do not know, but board member Andy4639 has considerable knowledge & experience.
Here's his take on the subject, quoted from my old thread when I was having alternator issues:

Just some food for though.
A 1 wire alternator will work but it want have the capability to control the charge like the 3 wire.
A 1 wire will charge at the same amount no matter what the load is on the battery are the rpm of the motor, where a 3 wire will only charge at a rate enough to keep the battery at a constant charge so it want ever under charge it are over charge it.

http://67-72chevytrucks.com/vboard/s...d.php?t=772236

[MARKDTN]

You really want a 3-wire. A 10si or 12si are both fine. The 12si is the later style with a little better cooling. For the lower amps you are talking, both of these are fine. If you go around 100 or more you want to go to the CS style. I would not use a CS130 for a paperweight, but the CS144 is much better and reliable (for these you need to change from sepentine to v-belt pulley). For the 10si/12si an 1986 307 Oldsmobile application gives the connection up and 94A 12si. If you have a long water pump and passenger side alternator, maybe a 1976 C20 application. This is plug towards the drivers side 63A or 78A. Many places seem to be substituting 12si for these.

[57taskforce]

I’ve got the 63 amp 10si with a short water pump setup on my K20. No regrets at all. One of the better things I’ve done to the truck thus far.

[Andy4639]

A 95 Buick Riviera 94 amp alternator
If you want to clean the wiring up even more just strip the tape off of the harness going to the external regulator. Take the brown and red wire and cut them at the regulator. Then run them straight to the alternator. You want need the jumper and the other wires can be clip off Then take the old external voltage regulator out of the truck and toss it!

This alternator fits the drivers side factory bracket for a short water pump setup.

http://67-72chevytrucks.com/vboard/s...d.php?t=363034

[kwmech]

My 68 still has the original 37a external on it. Now that I said that it'll crap out next week

[OregonNed]

Mine alternator was acting up when I brought it home after buying. I went with a Powermaster brand and have been very happy with it. It is wired as a one-wire setup.

[NorCalC20LWB]

Thanks again everybody for such informative responses. This should almost be saved somewhere for future reverence, pretty much everything you need to know about 10SI vs 12SI, amps, 1 wire vs 3 wire, and upgrading using the existing wiring harness or going with a new aftermarket harness.