Alternator Roundback . couple questions please.

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Eworth

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Hello,

Can you make sure I'm on the right path and also answer a couple questions please?

Car: 1964 Dodge Dart, originally Slant Six
ENGINE: Now is a 1978 318 / 5.2
IGNITION HEI conversion and no ballast resistor
CHARGING: I have already routed the B+ to the starter relay and no longer to the Ammeter.

ALTERNATOR: Is a Roundback and has two FLD terminals besides the B+

Question 1: Being a roundback with 2 FLD terminals, what year range would this have been made?

Question 2: I know that one of the FLD terminals is supposed to be a + and other a -, which is which?

Question 3: Should I be using the replacement Voltage Regulator for the old charging system, like the VR128 or the kind for the newer charging system that has the flat rectangular look, triangle shaped plug with two posts?

I dont want to mess this up so I appreciate any step by step on guidance you can provide.

Kind regards,
Mark
 
Not sure when they went from round to squareback. About 73, 74 I think

We need a photo, why? Because some lazy rebuilders CONVERTED 69/ earlier alternators to "isolated field" That is the proper name.

If it is actually a "real" isolated field, the first ones came out in 70, with some rare "late 69" ones which I've never seen, except pictured on the internet. The earliest versions had THREE regulator terminals, which is why the 70/ later regulator connector is shaped the way it is

This one here (click the link, too large to post) seems to be an oddity. While it appears to be "factory" isolated field (dual field) it ALSO has a place (marked grd) for the 69 style grounded brush. I don't know if this is Chrysler, or aftermarket

http://www.urqualitysolutions.com/images/36-7019-3.jpg

Here's another "oddity", same or similar to above......two isolated brushes, and a place for a grounded brush. This one is set up for a grounded brush (on left) and is missing the second isolated brush (yellow circle)

index.php


Below is what the definitive 1970 / later roundback isolated field should look like.......two isolated brushes, and no place to mount a ground brush

attachment.php


Below is the hated, hateful, POS "rebuilder" modified. This started out being a 69/ earlier with a grounded brush. Rebuilders drill the hole shown here at 12 O'clock for the second isolated brush. This one still has a grounded brush

128306-500-0.jpg


Why post all this? Why does it matter? BECAUSE IT CAN be dangerous. Some of these "came through" with a grounded AND isolated brush, or with what 'appears' to be two isolated brushes. If you hook the blue ign wire to the grounded brush, "smoke happens."

If you are lucky and get the blue ign hooked to the other one, you are faced with horried overcharging, as the alternator is at "full output.
 
Question #2 Answer:
On an isolated field alternators, the field terminal connections can be switched so (+) and (-) or polarity concern is not necessary. The field is a coil around two convoluted end plates. The energized coil makes one plate N and the other S from an electro-magnet perspective, and from the edge spinning to the stator N-S-N-S..... because the mesh of the interlaced convoluted poles. So changing polarity would make it S-N-S-N.... but that makes no difference, since the rotor is in rotation. North follows South, South follows North.
 

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So, which of the two terminals is the + and the - ?
And do I use the newer 2 prong type or the earlier replacement vr128? Thanks
 
There is no + or - on the field. Either wire, electrically will work. You can ground one field and use your 69/ earlier style regulator, or you can add one more wire and use the 70 / later regulator.

EDIT.......I see the second field connection hidden there LOL

If you are not "resto appearance" correct, if and when you buy a new / rebuilt one, get a squareback instead of a roundback
 
Will a square back mount exactly as the round back with the same brackets? And hook up the same I suspect.
 
And where do I find a quality square back. Everyone mentions not to buy a parts store remanufactured. Are people buying aftermarket alternators? Who do I buy one from?
 
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