I've seen round backs in 2 configurations, 2 field connectors and 2 but with one not having a tab, is the one without a tab (pic) older for the black box V-reg and the non tab being internally grounded??
Alternator/V-reg type?
- Thread starter Armyvet25
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Vaanth
Well-Known Member
The pictured alternator is the single external field connection version used in 1960 - 1969 applications. From the visible marking, the rear end shield (case half) appears to be ~1964. The electro-mechanical regulator was used with these alternators. In this case, one side of the rotor is grounded internally to the alternator and the regulator switches 12 volts to the external terminal to perform charging system voltage regulation.
A similar appearance alternator was released in 1970 with different field connections. This new "Isolated Field" alternator still used the "round back" style end shield although it is slightly different without the grounded brush. Two isolated field connections were now used. This style case was used through 1971. The voltage regulator changed to the two terminal solid state version. In this case, the rotor is isolated from ground with one side of the rotor powered by the ~12 volt Ignition Run circuit, and the other field terminal is a switched ground to perform charging system voltage regulation.
In 1972, the rear end shield design changed to the "square back" design, with a different rectifier structure, capacitor, and stator connections. but otherwise operated the same as the 1970 - 1971 version.
For more information about the Chrysler Alternators, refer to the following:
The Chrysler designed aluminum housing alternator was introduced in 1960 on the Valiant and Lancer models. This alternator had the informally termed "round back" style rear end shield. Chrysler called the two housing, or case, components "end shields". These alternators have one grounded brush and one field connection. This style continued through 1969 with a slight change in the spacing between the fins when comparing earlier Essex built versions and later Chrysler built versions. These alternators were used with an electro-mechanical voltage regulator. This regulator functions by switching +12V DC on and off to the alternator field lead to regulate system voltage.
In 1969, a special alternator was used with the new transistorized regulator in some models. This is the "Insulated Brush" alternator that looks much like the regular alternators of 1969. The difference is the grounded brush of the prior and other 1969 alternators is insulated from the rectifier, or back, end shield. The 1969 only transistor regulator looks like the 1970 and later regulators with the addition of a third terminal lead called the suppression lead, in addition to the ignition and field terminal leads. Other 1969 models not so equipped still used the grounded brush alternator and electro-mechanical voltage regulator.
In 1970 models, the alternator and voltage regulator were again redesigned. The new "Isolated Field" alternator still used the "round back" style end shield although it is slightly different without the grounded brush. Two isolated field connections were now used. This "round back" style was used through 1971. The voltage regulator now contained only two terminal leads, ignition and field. This is why the triangle shaped connector looks like it is missing a lead, because it is. The connector and regulator case are carryovers from the 1969 transistorized regulator with different internal electronics. The regulator functions by switching ground on and off to one alternator isolated field lead with the other field lead connected to +12V DC (Ignition Run). The regulator action is adjusted for temperature too. This regulator was used through the 80s on cars (with a change in 1975 for the different 100 Amp alternator, a slight revision in 1980, and some other slight application variations), and early 90s in trucks.
For the 1972 models, the rear end shield was redesigned in the informally termed "square back" style. The end shield contained a different mounting for the rectifiers and capacitor and connected to the stator without soldering. This change simplified assembly and service operations,and improved alternator reliability. The electrical functioning of the alternator remained the same with the "Isolated Field" introduced in the 1970 models with the "round back" style case. This particular "square back" style was used through 1977.
For the 1978 models, the end shields and stator were redesigned again. The most visible difference is the "thin" edge of the stator between the two end shields. the end shields and stator were redesigned again. The most visible difference is the "thin" edge of the stator between the two end shields. but is available in higher capacities than earlier models. This alternator style was used from 1978 through 1987. These alternators can interchange with the earlier versions, but some alignment adjustment might be needed.
Excerpted from "Chrysler Alternators, 1960 - 1989", Gary Lewallen, aka Vaanth
thought so, wanted confirmation, a great big help and super Thank You!!
I know a lot of people upgrade from the single field black box to the solid state 2 pin, did the old style work well? I've got a real thumper of a cam and lower rpms at idle for reference. Trying to keep what I have vs buying a single wire alt, which may happen eventually
Vaanth
Well-Known Member
In general, the 1960 -1969 electro-mechanical voltage regulator and single field connection alternator works fine. The 1970 and later system provides for more consistent charging, and has built in temperature compensation to raise the charging voltage a little when cold, and lower it a little when hot, for better battery charging and life. The electronic regulator is maintenance free. Early and later alternators are roughly equivalent in durability, but overall, the later alternators can have nominally higher output. Electronic replacements are available for the older system voltage regulators without changing the alternator or wiring, and many modern replacements are only available in this format, although quality can be in question.
Comparing the two systems is similar to comparing point ignition to Chrysler electronic ignition. Electronic is more consistent and less maintenance with no points to wear or burn and provides consistent, but largely fixed, dwell. Electro-mechanical regulators have points to wear and require possible adjustment for conditions. Both do the job though.
Most Chrysler alternators prior to 1978 can have low idle output, albeit adequate, but marginal in some load cases, in a stock matched system. This could be compounded with a lower or more erratic idle from a more radical camshaft, or other effect. The electronic regulator and matching alternator can provide a little more stability in this situation. Ensuring the wiring, connections, etc. are in good health ensures a possible low idle output is minimized. Selecting a comparable, but higher capacity, stock alternator can help, such as replacing a factory 34 amp unit with a factory 60 amp unit. Attention to wiring is required, but generally, within the 34 to 50 amp range requires no changes. 60 amp wiring can vary. Getting into the 65 to 78 amp standard alternators requires wiring adjustments. Leece Neville, Motorola, or later Chrysler higher capacity alternators used in fleet applications and other high demand applications require greater modifications. Aftermarket high capacity alternators are a different game, but I don't use any of those.
Although the earlier system is fine for a matching stock system, I have changed all of mine to the later system as a matter of course as a preference, and because I have the parts. I only use older stock or near stock American made stuff though. Some of my vehicles have the factory Chrysler 100 amp alternator system. I have converted a couple of trucks to this system, but due to the alternator size and brackets, I likely wouldn't convert a car to this system, unless it was a police application, or similar. Conversion requires wiring changes and attention to the ammeter and connections, in addition to the specific brackets, etc.
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I ordered the black box since it's compatible with my alt, will upgrade to single wire later
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