Alternator Wiring-2nd Question

[Shoebox]

While reading up on the installation of an alternator in my '51 Tudor converted to 12v neg. ground, I came across the mention of a situation where a car may not shut off with the original ign. switch due to current back flowing because alternators produce current even at idle,...... OR SOMETHING LIKE THAT Anyhow, a component called a DA Plug was recommended and I got one. 18 years ago I did the same 6 cyl to V8 swap that I am doing now on a '51, and used a 6v pos. ground alternator, and I don't REMEMBER needing such a component. I must confess, there are many things I don't remember from 18 years ago (or what I had for lunch yesterday) but I am wondering if any of this makes sense to those who have done something similar? See pic of this DA plug on my alternator. Thanks guys!

[rich b]

That DA plug incorporates a diode in the wire which acts as a one way valve letting electricity from the ignition switch go to the alternator to excite it; but prevents electricity from the alternator going back to the ignition switch and onto to the coil enabling the engine to continue to run when the switch was turned off.

Same thing can be accomplished with an "idiot" light in place of the diode.

[Ggmac]

I’m not sure you always need it . If you have a generator idiot light , the engine won’t run on . If I remember correctly.

[Shoebox]

Rich and Ggmac, thanks for the answers, there might be an idiot in the car but no idiot light,.... so I'll be using the DA plug.

[V8 Bob]

The DA plug designed for regular production 10/12SI GM alternators has two numbered wires:



#1- Goes to the ignition switch (on) and should have a diode/and or idiot light (a common #194 indicator works great) in series to prevent run-on when shutting off. This light will also warn of low charging issues.


#2- This is output voltage monitoring that goes to the same distribution lug/location the main feed from the alternator goes to, NOT the battery. This ensures the approx. 14.4V output of the alternator is at the distribution point and not just at the rear of the alternator, to eliminate/minimize any voltage drop. This is especially important with rear battery locations, like two of my cars.


I don't know about your Powermaster, but the one I bought a few years ago was labeled one OR three wire, and it came with a DA plug. Curious how the regulator can operate one OR three wire, I talked to their tech support and found out the operation is ONE wire, but allows a stock production vehicle DA to be plugged in, without voltage monitoring. I then sold the Powermaster and bought a rebuilt 3-wire 12SI from our local re-builder in town for about 1/2 the cost because I wanted the advantages of 3-wire operation.


So, I'm not sure if your #1 DA lead will function with a diode or a #194 lamp, because the one I had would not.


You might want to learn more about the advantages of a GM 3-wire 10/12SI like I did, through the text and pictures provided by Mark Hamilton @ M.A.D. Enterprises.

http://www.madelectrical.com/index.shtml



Actually they are 4-wire, because of the suggested and important case ground.


IMO, the ONLY advantage of a one wire is less /easier wiring. These were designed more for constant rpm/stationary usage, not automotive.

[Shoebox]

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"You might want to learn more about the advantages of a GM 3-wire 10/12SI like I did, through the text and pictures provided by Mark Hamilton @ M.A.D. Enterprises."


During the building/wiring of several previous project cars (2 of which had trunk mounted batteries) I had the opportunity several times to speak with Mark Hamilton on a variety of subjects, including the advantages of GM 3-wire 10/12SI. I went that route on those projects, on this '51 I'll shamelessly admit I'm opting for some simplicity. Big thanks as I appreciate the input!

[tubman]

I had a one-wire alternator (with the diode add-on) on my old '36 because I wasn't aware of the difference. Never had any sort of problem with it, though.

"Ignorance is bliss."

[wga]

Reading your post, I thought of Mark, and his thoughts on 1 wire vs 3 wire.

1 did the 3 wire on IHC L110 6 cylinder engine (SD220) using a 10Si alternator.
No problems with it.

On my 49 using a 1 wire and no issues.