stellar

It looks more like a 10SI to me. It may even be the late 10DN style, but I can't tell from the pic. Are the alternator plug terminals like this l l or this - -?

ReallyWildStuff

I made more photos. This is (apparently) an internally regulated alternator, but the standard red/white molded plug (as shown far above in this post) does not fit into it.

https://flickr.com/photos/78849780@N00/sets/72157677691657172

i apoogize to the OP for glomming onto their thread.

MDchanic

So, Stellar, as the resident expert, what do you think? 10si?

I am definitely not up on these lesser-seen beasts.





- Eric

stellar

Late 10DN external reg type. I am guessing to stay at 14.4 volts the engine was not reved much, because the alt was probably being full fielded. Had it been run for a longer time or at higher revs it would have overcharged. The alt is probably of 1972 vintage.

MDchanic

So, dumb question, but to confirm my belief:

Regardless of exact case appearance or whether the terminals are at the back or the edge, if the terminals are ( | | ), then it's a DN / externally regulated type, and if they terminals are ( — — ), it's an SI / internally regulated type.

Have I got it right?

Thanks!

- Eric

stellar

Yep you got it. There is another 10DN that looks nothing like this one or the early one you are familiar with, but it was used on trucks and equipment, so you will probably never see one on a car. It has a different mount.

olds 307 and 403

Yes, there parts will interchange. The better fan and more open back help cool the 12si, the high amp 10si alternators get very hot, my 100+ amp model lasted 5ish years. I had a 100 amp, that probably put out closer to 80 amp that just needed a regulator change in the 10 years I owned it before the truck burned.

stellar

10 dn and 10si ends 001.jpg

10 dn and 10si ends 002.jpg

10 dn and 10si ends 003.jpg

10 dn and 10si ends 005.jpg

10 dn and 10si ends 004.jpg1st 2 are a 10dn you may never see. 2nd two are the late 10dn rear end plate that is similar to the 10SI shown in the last 2 pics. Notice the small difference where the opening is for the plug on the late 10dn and the 10SI. There is a small support post for the internal plug where the external case has no support post. If you would interchange housings, the 10SI post would need to be removed to accomodate the external plug. Some of the early open faced rear housings are different than both of these in this location besides the rear fins, but that is another story.

joe_padavano

Yeah, I was going to say this is the oddball 1972 "transition" alternator that was essentially the 10SI case with the 10DN internals.

ReallyWildStuff

Thanks to all. This is definitely "not the alternator I want or need".

I will replace my test stand equipment with a more typical 12si model and return this "c.1972 externally-regulated late 10dn" alternator to my friend so marked.

Is this particular "late 10dn"-style alternator worth more to an Oldsmobile restorer re: rarity? What specifics can I look for after removal to identify it more specifically?

Thanks again for all the expert help. I don't know anything about externally-regulated anything, didn't mean to imply that I did, and regret being able to "hook it up anyway" despite my ignorance on the topic.

What would in fact happen if this alternator were spun at high RPM for extended times without a regulator? As shown the alternators's positive post is wired to the ignition switch, battery, and to alternator terminal #2. Terminal #1 is wired to voltmeter.

I swear the volts did NOT track up above 14.4 with momentary revs up to approximately ~2k. This isn't a dyno stand, so I'm not doing any pulls or anything. Almost 100% of the use was at idle only.

Thanks

stellar

It may be worth something to an olds buick or chevy owner depending on the number on the front case. As it was wired it would overcharge. Some batteries will take a bit more to overcharge. The battery may have been a bit low and didn't have enough rpm or time to show the overcharge. The volts if connected to the #1 terminal should have been in the 7-8 volt range, so it is possible you also have a bad diode in there. Post the number on the front case, and I will try to give you a make and model for it.

ReallyWildStuff

I finally took the weirdo alternator off. I put more photos in this album:


Does anything point to its definite ID?

I see:

"10" on the back of the rear case
These numbers on the edge of the front case:

1100946 55A
3H8 12VNEG

Thanks for the help -

Brian in Houston

ReallyWildStuff

I can't find a definite ID for 1100946...suffice to say it is not super-rare.

3H8 is:
1973 August 8

So the front housing was originally from a c.1974 or later vehicle, correct?

My research shows that GM alternator production was "all SI" (Systems Integrated = Internally Regulated) by 1973 - and yet this alternator definitely has DN-style connections.

Again, its performance on the stand was indicative of being "internally regulated" and "100% functional" (14.4 Volts)

Weird.

stellar

1100946 Buick apollo. Front hsg has been switched

ReallyWildStuff

Thanks. So, the $64k question:

Is it physically possible to have an internally regulated alternator that presents with the DN-style plugs? All my info points to this alternator being of that kind.

This would be as for a "stealth" retrofit on a car that was originally externally-regulated - looks like a DN (accepts the factory DN plug) but functions like an SI.

This alternator's owner is a 65-72 A-body guy. This alternator is "not appropriate" for my '77 D88 wiring regardless (SI plug won't fit in the DN hole).

Thanks

stellar

Anything is possible. I doubt if this has an internal reg making it a stealth alt. I could probably make you one if you want one, but I see no reason for it. I think your info pointing to a stealth alt is wrong. Open it up and take a pic of the inside and we can tell you for sure.