Alternator

[RichardJ]

>>"flash the field"<<

An interesting term to use when you are talking about an AC Alternator.
If we were talking about a DC Generator that term would make more sense. When discussing a DC Generator, someone will always mention Polarizing the Generator.

In the first image below there are Iron Pole Pieces used in DC generators, The Field Windings are wrapped around these Pole Pieces.
These Iron Pole Pieces retain a great deal of magnetism. The Polarity of the magnetism retained in these pole pieces is crucial to the correct operation of a DC Generator.
When working on a DC Generator, it is common for the polarity of the residual magnetism to be reversed.

It is then very important to correctly align the magnetic polarity of the pole pieces, with the Polarization procedure.

AC Alternators do retain some residual magnetism, but the polarity is not an issue.

In the second image, the ignition switch connects 12V from the battery, through the voltage regulator, directly to the field winding. Full Field magnetism is generated and current begins to flow in the Stator Windings. This ignition circuit is called a Exciter Circuit.

Full Field magnetism is generated the moment the key is turned ON and also at idle. Field magnetism is reduced by the voltage regulator, as max voltage is reached.

[RichardJ]

>>The theory behind this is a perfect wire with perfect connections will not drop voltage so the meter will read zero volts.<<

All copper wire has resistance to electrical flow. The fatter the wire, the less resistance, the lower the voltage drop from one-end-to-the-other.

Chevy relies on that voltage drop on the wire between the Alt and the Battery. That is the basis of the design of the Ammeter circuit.
The greater the Alternator output, the greater the Voltage Drop on that wire, the greater the Ammeter indication.

The type of Ammeter used in these trucks must have an External SHUNT.
In this case the Charging wire serves doubly duty and is also the Shunt Wire for the Ammeter.

Other Ammeters contain an Internal Shunt. This '67-72 Chevy Ammeter does not.

[HO455]

Originally Posted by RichardJ

>>"flash the field"<<

An interesting term to use when you are talking about an AC Alternator.
If we were talking about a DC Generator that term would make more sense. When discussing a DC Generator, someone will always mention Polarizing the Generator.

In the first image below there are Iron Pole Pieces used in DC generators, The Field Windings are wrapped around these Pole Pieces.
These Iron Pole Pieces retain a great deal of magnetism. The Polarity of the magnetism retained in these pole pieces is crucial to the correct operation of a DC Generator.
When working on a DC Generator, it is common for the polarity of the residual magnetism to be reversed.

It is then very important to correctly align the magnetic polarity of the pole pieces, with the Polarization procedure.

AC Alternators do retain some residual magnetism, but the polarity is not an issue.

In the second image, the ignition switch connects 12V from the battery, through the voltage regulator, directly to the field winding. Full Field magnetism is generated and current begins to flow in the Stator Windings. This ignition circuit is called a Exciter Circuit.

Full Field magnetism is generated the moment the key is turned ON and also at idle. Field magnetism is reduced by the voltage regulator, as max voltage is reached.

Thank you for posting such a thorough explanation of this.

[HO455]

Originally Posted by RichardJ

>>The theory behind this is a perfect wire with perfect connections will not drop voltage so the meter will read zero volts.<<

All copper wire has resistance to electrical flow. The fatter the wire, the less resistance, the lower the voltage drop from one-end-to-the-other.

Chevy relies on that voltage drop on the wire between the Alt and the Battery. That is the basis of the design of the Ammeter circuit.
The greater the Alternator output, the greater the Voltage Drop on that wire, the greater the Ammeter indication.

The type of Ammeter used in these trucks must have an External SHUNT.
In this case the Charging wire serves doubly duty and is also the Shunt Wire for the Ammeter.

Other Ammeters contain an Internal Shunt. This '67-72 Chevy Ammeter does not.

And thanks for adding clarity to the charging circuit operation.
What would you expect the voltage drop on the Shunt wire to be on a stock system at idle with all the switchable loads turned off (i.e. wipers or headlights)?

Hopefully the OP will be able get things back to normal.

[Minkota]

Originally Posted by HO455

Hopefully the OP will be able get things back to normal.

I was able to get it to charge at an idle by bumping up the idle by about 150rpm. Seems to be working fine now when idling at around 850-900 rpm.

[HO455]

That is good to hear. Congradulations!

[RichardJ]

>>bumping up the idle by about 150rpm............... idling at around 850-900 rpm.<<

That's not what I would consider a solution. I wouldn't even consider 850-900 as an acceptable idle rpm. That's the rpm I would expect on the 1st or 2nd step of the High Speed idle cam mechanism.

Earlier in post #16 you said you had 14.7V at cruise and 13v at idle.

What is wrong with that?

When you are talking about an automatic with an idle of 850-900 rpm, you probably have 150-200 rpm difference between Drive and Neutral. To me that is completely unacceptable.
Having to BANG a transmission into drive, because of an incorrect idle rpm drives me crazy.

[Minkota]

Originally Posted by RichardJ

What is wrong with that?

at idle it would drop as low as 12.3 volts.

[RichardJ]

In post #16 you said 13V.
In post #30 you said you bumped the idle 150 up tp 850.

Are you now saying your new 12SI is providing 12.3V at 700 rpm?

In post #11 you provided a picture of the old 10DN alternator. What was its output voltage , at what idle rpm?

Unless you have a high load at idle, it doesn't sound like the new 12SI is working properly.

[kenn]

Hello I think I will need this later.

[Minkota]

Originally Posted by RichardJ

Unless you have a high load at idle, it doesn't sound like the new 12SI is working properly.

I took the alternator back to be tested and it failed. Put a new one on and it’s working perfectly.

[Steeveedee]

That seems to be a common problem with rebuilt stuff these days. I've replaced the rebuilt alternator on my truck twice, now. Both times for bad diodes.

[Minkota]

Originally Posted by Steeveedee

That seems to be a common problem with rebuilt stuff these days. I've replaced the rebuilt alternator on my truck twice, now. Both times for bad diodes.

Mine was supposedly a Brand New Unit, which is why i was thinking it was not the alternator at first.

[Steeveedee]

Originally Posted by Minkota

Mine was supposedly a Brand New Unit, which is why i was thinking it was not the alternator at first.

I would not have expected that, for sure. More and more poor quality stuff is produced, anymore.

[Minkota]

Since installing the new alternator, i am experiencing a pretty bad battery drain. is it possible that it is from the way it is wired?

I connected the 2 outside blue and brown wires at the regulator.
I connected the 2 wires at the alternator plug what would be the brown and white wires (previous owner made them them the same color wires black) and connected both of them to the White wire on the ne 12si plug. I feel this might have been wrong.
I ran a new 10ga wire to the battery from the the big red bolt on the back.
I ran a new 10ga ground wire from the alternator housing to the ground on the battery.

[RustyPile]

Originally Posted by Minkota

Since installing the new alternator, i am experiencing a pretty bad battery drain. is it possible that it is from the way it is wired?

I connected the 2 outside blue and brown wires at the regulator.
I connected the 2 wires at the alternator plug (previous owner made them them the same color wires black) and connected both of them to the White wire on the ne 12si plug. I feel this might have been wrong.
I ran a new 10ga wire to the battery from the the big red bolt on the back.
I ran a new 10ga ground wire from the alternator housing to the ground on the battery.

Don't just assume the drain is caused by the new alternator.. Using good troubleshooting techniques, track it down.. There are numerous threads and posts explaining how to do this and how to modify the wiring for converting from an external voltage regulator to an internal one, so I won't go over that again..

[pjmoreland]

I installed a 12SI alternator a few months ago. Initially, I had the wires swapped at the alternator, and this created a battery drain. Here's how I have the wires connected now. The original voltage regulator had the following four wires connected to it:

brown
red
white
blue

I purchased a jumper that plugs into the harness in place of the voltage regulator, and it connects the following wires together:

brown to blue
red to white

The blue and white wires then run to the alternator and connect, as follows:

blue - 1
white - 2

Another way to say this is:

regulator brown connects to alternator pin 1 (uses blue wire)
regulator red connects to alternator pin 2 (uses white wire)

[LNP]

I went with a 100amp one wire alt. This made things simple.

[xs-cash]

Originally Posted by LNP

I went with a 100amp one wire alt. This made things simple.

Where did you hook up the one wire?

[68 TT]

Originally Posted by MARKDTN

I would do a couple of things in your situation. I would get rid of the factory ammeter and go to a voltmeter. I would change to a CS144 (I would not use a CS130 as a paperweight). Delco #8077 pigtail is used if you have a lamp on the dash and the #8078 has a load resistor for use with no lamp to go from SI wiring to CS so you will have to do some adapting(different plug at alternator, but can use the same sense wires). Application for a 140A CS144 is '95 Buick Roadmaster. Then I would add a bigger wire from the alternator output to the battery. I might also add a junction block near the battery to power the fans and amp, that way you don't add any high loads to the original harness. While I was wiring, I would add headlight relays as well (to get brighter headlights and take load off the original switches and wiring).

If you don't want a CS144, then a 12si in either 78A or 94A. Anything bigger may have cooling issues. The 84-85 Corvettes do have a 12si that is 120A, but I would go CS144 if I wanted over 100A. 94A 12si is Delco 321-269 application '85 Riviera with 305Y, HD cooling and a/c. 78A 12si is Delco 321-244 application '85 Cutlass Supreme with 305Y. Nothing wrong with a 10si, I would just get a 12si if I was making the change since they have improvements. Don't use a 10si fan on a 12si, you have to get the 12si fan so be sure what you buy has the fan on it.

I agree, the CS130 is an overheating pile of junk that is a ticking timebomb of a roadside breakdown waiting to happen. The CS144 is a whole different animal and is a great design. I retrofit them into everything I can make them fit into. For 180-degree ears a 1996 Impala SS application is 140-amp and for serpentine accessory drives with 90-degree ears a 1999 Tahoe has a 140-amp CS144 as an option. If you can't make a CS144 fit then the 12SI is a great upgrade from the externally regulated stock part. A 1984 Z/28 with the HO 305 has a 180-degree ear 94-amp 12SI that fits great into classic muscle car brackets.

[LNP]

Originally Posted by xs-cash

Where did you hook up the one wire?

The only wire I use is the battery wire from alt to battery. This setup will not
have a place to hook up a warning light. I have a volt gauge in my dash instead
of a amp gauge