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Wiring diagram for the GM HEI coil/module/bracket?
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Author:  pneps [ Tue Feb 19, 2008 11:42 am ]
Post subject:  Wiring diagram for the GM HEI coil/module/bracket?
Need a wiring diagram for the above. It is the all in one type bracket with attached coil and module, used on 96-2000 trucks and SUV's .

I have seen it before on here but now cannot find it, even using the search function.

Help is greatly appreciated.
Author:  dudley [ Tue Feb 19, 2008 12:01 pm ]
Post subject: 
GM HEI Ignition for Mopars (free)
http://duster318.freeservers.com/tech/hei.html

SAE Technical Paper (for pay)
https://shop.sae.org/technical/papers/750346

Topic: HEI Electronic Ignition Retrofit How-To
http://www.slantsix.org/forum/viewtopic.php?p=101013
Author:  SlantSixDan [ Tue Feb 19, 2008 1:25 pm ]
Post subject: 
If you're talking about the combined coil/module unit pictured here , connections to the module are as follows:

Image

I can't find a similar diagram for the coil, which has three terminal pins.

"A" is the coil's primary (+) terminal; gets ignition-on 12v and is connected to module pin "A".

"B" is a tachometer signal output. Not used if you don't have a tach.

"C" is the coil's primary (-) terminal, goes to module pin "D"
Author:  pneps [ Tue Feb 19, 2008 5:57 pm ]
Post subject: 
OK, so the A term will go to a switched battery voltage, B&C terms will be the two wires coming from the distributor, and D term back around to the coil, Correct??
Author:  SlantSixDan [ Tue Feb 19, 2008 7:04 pm ]
Post subject: 
That sounds right to me. The only thing I'm not quite sure of is whether module-C is the signal ground, or the module ground. I am guessing that you're correct and the module ground is obtained via the mounting...but actually now I think about it, it shouldn't matter, because the pickup coil and the module should theoretically be on the same ground plane. We need 440_Magnum to come and look this over. I'll see if I can roust him up.
Author:  440_Magnum [ Wed Mar 05, 2008 12:56 pm ]
Post subject: 
Quote:
That sounds right to me. The only thing I'm not quite sure of is whether module-C is the signal ground, or the module ground. I am guessing that you're correct and the module ground is obtained via the mounting...but actually now I think about it, it shouldn't matter, because the pickup coil and the module should theoretically be on the same ground plane. We need 440_Magnum to come and look this over. I'll see if I can roust him up.
Sorry for the very late "rousting." I didn't notice that "you have a new message" thingy :-/

And I'm afraid I don't have a lot to offer. The only HEI I'm familiar with is the old 4-pin style that takes module ground through the case. My guess is that "C" on this one is a redundant ground since the coil itself also has to be grounded. To be safe, I'd ground both the case and pin C as securely (short wires if possible) to prevent trouble.
Author:  Matt Cramer [ Wed Mar 05, 2008 5:02 pm ]
Post subject: 
I'm pretty sure it is signal ground as the pick-up was always connected to the module. I don't think I have ever seen or heard of a HEI module that had the pick-up coil grounded separately from the module. Maybe I ought to check a module to see if they really have the same ground plane - they may not.
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