The Stovebolt Site Forums The Shop Area The Electrical Bay Alternator wiring schematic

I know, this topic has been discussed A LOT. I have a 58 chevy apache (1/2 ton) and I pulled out the stovebolt. I put in a Chevy 350. The 12V generator is now gone, and an alternator has taken its spot. I am looking for a wiring schematic that is for a 3 wire alternator w/internal regulator. How do I bypass the external regulator and get power to the cab? Is there a wiring schematic that will make this any easier? Should I not use the original harness? Please help!

---Casey

I don't have a schematic but all you have to do is take a heavy guage wire (at least a 12 ga.) and run it from the alt. output lug to your old regulator's "BATT" terminal, you can use the terminal as a junction block. Take the other 2 wires off the old regulator and just tape them back.

On the alt. the DA plug's #2 terminal (sensing) can loop right down on top of the output lead. #1 is usually not hooked up unless you have "idiot lights" and I can't remember if your '58 uses those or still had the ammeter.

IMO, unless the alternator is spec'd with the proper regulator for single wire service, DA#1 must be connected to a switched power supply for the unit to produce a charge. If a charge lamp is in that circuit then that's a plus, but not required.

10SI alternators with single wire 'self exciting' regulators need no connection through the DA plug (regulator).

If the alternator is purchased from a supplier based on application it will probably not have single wire capability. If it were purchased from a local auto electric rebuilder then it may have the 'either/or' regulator installed.

This has been my experinece.

http://www.weblube.com/10SI-regulators2.html

Stuart

I have to admit Stuart that I'm still a little confused about DA#1. It was stated on here a few weeks ago that only the very earliest versions of Alts. needed to be externally excited with a "switched hot" lead. It was further stated that any of the alts. made in the last (and I forget the number of years here but it was a LOT) years would self-excite with residual magnetism.

I sure would like to get this settled once and for all in my little pea-brain!

Don,

I don't know the answer to this conundrum! No 10SI came with a regulator that allowed single wire use(stock). There are aftermarket brand regulators available that rebuilders utilize that will allow single wire use OR three wire connection. The rebuilders often stock only this one regulator as 'one size fits all'.

If you were to purchase a alternator from a auto supply house and it was called out for application, I don't know if it would have the 'one size fits all' regulator...maybe that's all they make these days.

If your regulator isn't the type capable of single wire service then your alternator isn't going to charge until DA#1 is connected and energized. It's pretty easy to diagnose but we haven't seen any feedback from the folks asking these questions.

That's about all I think I understand on this topic...

Stuart

No alt. starts with residual magnetism. Generators do. Stuart is correct, you need to energize #1 or it won't work.

Isn't one of the original wires for the generator a switched power source?

The internal self igniting regulators are around $15 or $20, and make hooking up alts way easer. On a recent job I did, we used the factory heavy generator wire hooked to the old regulator Batt. terminal along with the original wire coming from the cab. The alternator charges great, uses stock wires and the amp gauge worked as it should.

Joe

The old external regulator alt. had a wire comeing off the ign switch but the gens. didn't. They started with residual magnetism.

Sorry if this seems redundant but I'm still befuddled by the DA#1 question.

Jerry posted this awhile back, no mention of residual magnetism (my bad on that) but it would seem as though only certain early versions of the 10SI needs to see 12V on #1.

Again , not trying to belabor the point, just trying to get a clear picture of this in my head.

I was completely satisfied with waldo53's comment. Now that it is clear that his instruction was incorrect, I'm an utterly confused once again.

I found this article on this website (at the very bottom of the page http://www.stovebolt.com/techtips/12_volt_conversion.html )

It talks about the conversion, but doesn't say if the alternator is one wire, or three.

What does this step mean:

Take the "Batt" wire that used to go to the regulator and connect it to the red wire of the DA plug. ???

What Batt wire is talking about?

Casey; with all due respect to other posters on this thread I'm not convinced my "instruction was incorrect". Did you hook it up and try it?

If you wired it like I originally said and it doesn't work, then also run a switched hot lead to DA#1 and it should work.

Keep us posted on what happens.

Lol, Ok. I will. Since I understand what you wrote, I will do just that! I'll report back the results---

Casey

Below are a couple of links that show some examples of how to rewire generator systems to internal reg alternators. The first rewires a Buick with generator and a Buick with external reg alternator. It also provides a lot of additional info and links.
http://www.rowand.net/Shop/Tech/GeneratorToInternallyRegulatedAlternator.htm

This second one is for Corvairs, but they use the same generator, same regulator and the same wiring if your '58 Apache has a generator (idiot) light. Generator conversion on top and ex-reg Alt conversion on the bottom.
http://autoxer.skiblack.com/nallm/ireg.jpg
If your truck has an idiot light, it will be wired very much like the drawing in the top, left. In the middle of that drawing, is a plug called a "main harness connector". The wire from "A"( or "GEN") on the regulator goes through that plug to the "GEN" light in the dash. The other side of the "GEN" light goes to 12 volts when the ignition switch is switched "ON". From the ignition switch, it is connected back through the "main harness connector" to the "Bat" post on the regulator.

From the second drawing in the first link, I would like to point out a couple of things.
http://www.rowand.net/Shop/Tech/images/AlternatorWiringSchematic-1974Buick.jpg In the lower right you will see a wire labeled "24 brown/white (resistor wire (10 ohms)". This resistor is in the wiring harness for vehicles with the 10DN External Reg Alternator and the 10SI or 12SI Internal Reg Alternators. This resistor is in parallel with the "GEN" lamp when the ign key is "ON". It is there so that if the "GEN" lamp should fail, the circuit will still be complete. You do not need it, BUT a 10 ohm 10 watt resistor from Radio Shack wired in parallel (across) the "GEN" lamp will do the trick. I think it should be included, but most people don't bother.
This "GEN" lamp connects to post #1 on the Alt and it is the Exciter circuit.

On the top left of that drawing you will see a "10 Black/red" wire that connects #2 on the Alt plug almost directly to the Batt post on the Alt. This is the "Voltage Sensing wire" for the voltage regulator. If you have read the MadElectric web page, he explains in detail why this is not the best place to connect the sensing wire. In the next drawing you can see that the "Sensing wire" is connected closer to the battery, where it should be.
http://www.rowand.net/Shop/Tech/images/MergedWiring-1958Buick-InternallyRegulated.jpg

Waldo was totally correct, about the residual magnetism. Take another look at post #1 in the drawing. Internally the post #1 connects to the voltage regulator then the field. Also connected to #1 internally is the feed-back circuit from the diode trio. As was pointed out, the residual magnetism is minimal, but if you rev the snot out of the engine the stator can generate enough voltage through the diode trio to do what the Exciter circuit is supposed to do in the event you don't have it connected properly.

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml does a great job of explaining all of this and a lot better than I ever could.

Hi Waldo,

Thanks for all of your responses on my post "Alternator Wiring Schematics." I am currently getting all of the wiring together and almost to point of installing the alternator.

I have an additional problem I was hoping you might be able to help me with. What is the main battery source to cab? In other words, which wire powers the cab?

I can get power to cab, but I'm not sure it's the right wire because the power is constant top the cab even when the key is out of the ignition! What regulates power to cab so I don't run my battery out when the truck is off? Or, is there always power to cab in these older trucks?

Any help would be appreciated!

---Casey, Rat Fink

Richard, I have used Mad Electrics schematics on three trucks so far, 2 53 PowerWagons, and a 53 5700 COE. I used the powerpoint he describes and it works nice-- headlights so much brighter, and the system charges like it was designed to do based on load applied. That was the reason I have never really liked the single wire system although it is very simple to install.