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Because I use a GM 12si alt, this is a different HEI questio
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Author:  rock [ Sat Jan 19, 2008 3:08 pm ]
Post subject:  Because I use a GM 12si alt, this is a different HEI questio
OK, Dan and all,

I have been studying the long thread and all its references for weeks. I have sketched all my wiring since I rewired completely, and none of the questions to date address my quandry. Using a GM alternator and a Pertronix allowed me to, in essence, separate the charging from the firing circuits. I even have the alternator low on the driver side and the ignition on the plug side. I am going to try out the Mopar HEI with 4 pin GM module as Dan detailed. But since the GM is internally regulated I have no wire going to the IGN thence to FLD on the firewall regulator, because I don't use it. I do use the resistor

My stock diagram before doing all new wiring shows I had at the beginining, three ballast resistor wires as follows: a single wire on one resistor terminal going to the FLD terminal on the stock firewall voltage regulator, and a pair of wires in a plug on the other resistor terminal....one going to the IGN switch "only on at engine start", the other to the coil positive. In the "ALL NEW" with GM, I of course DON't USE the fire wall regulator at all.

Now, Dan and you other fellows use the GM module on a Mopar alternator by connecting the wires together that are on the resistor and no longer use the resistor. The GM 4 pin module then has black and red from coil on one side and black and red from distributor on the other side. HOWEVER, you are using the MOPAR alternator with a FLD wire still attached to the firewall voltage regulator, thus ultimately when the resistor wires are connected together, they are connecting coil positve to IGN "only on when STARTING" terminal on the ignition switch, to FLD on the firewall voltage regulator.

Since with the GM I have run a wire from Terminal 1 to "only on at RUNNING" to turn on the alternator, it seems to me I can keep using the GM alternator as I have it now, i.e. regulating the alternator from Terminal 2 in my ALL NEW and turning on its field with "only on when running" from the ignition switch. This is like connecting the resistor wires as recommended.

But, what would I connect the coil positive to? the "only on when starting" on the ignition switch? I am wondering if the sole purpose of the GM HEI module istto tell the coil when to discharge, basically.

I hope you can follow this and feel you could answer with a quickie like coil + to ...etc. If not, and I am a guinea pig with the module to the GM alternator, I at least have good sketches to share.

Thanks
rock
'64d100
Author:  Matt Cramer [ Sat Jan 19, 2008 6:42 pm ]
Post subject: 
You have to tie the coil positive to both ignition terminals on the ignition switch, the one that's hot in Start and the one that's hot in Run. If you want the alternator to not charge when cranking, you will need to control it from a separate terminal (maybe ACC) on the ignition switch.
Author:  rock [ Sun Jan 20, 2008 5:39 am ]
Post subject:  Ahhh, Thanks Matt! Yes, and use a diode on the FLD on
Ahhh,

Many thanks Matt! You come through again on strange stuff. I realize I am so close to the problem it is hard for me to step back, and I hadn't thought about putting BOTH ignition switch terminals together to Coil +. I can then put a diode in the line running from the switch to the alternator FLD "turn on" and in effect use the diode as a one way switch to keep current flow from coming back the wrong way. Then I wouldn't have to use ACC as you suggest (GOOD thought!)

I thought orignally swapping to Mopar HEI would be a matter of "if using a GM alt. and a GM controller, why not turn it on and off like GM does?", but I couldn't "logic" out how to do it despite drawing diagrams for several weekends because I haven't been able to find the internal circuit schematic for the GM 4 pin controller. I was about to build a breadboard circuit on the bench with a spare ign switch, an alternator turned by an AC electric motor, and a GM module while using a logic probe and DC voltmeter to see what was going on..thanks for saving me the hassle.

rock
'64d100
Author:  Matt Cramer [ Sun Jan 20, 2008 6:04 pm ]
Post subject: 
It's easy to overcomplicate things. The best way to describe what is going on inside the HEI 4 pin module is that it's like a magical set of breaker points that changes its dwell angle as a function of RPM. It limits the current though the coil by changing dwell so there is no need for a ballast resistor.
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