I've thought about making up color-coded wiring diagrams focused on the alternator and voltage regulator for some time. The question came up again the other day on how and what the different wires were connected to.
So, I decided to do it, one diagram for cars without factory ammeters, one for cars with factory ammeters, and a bonus of a 3G wiring diagram.
If anybody spots any errors, please let me know, so I can correct it.
View attachment 40168
EDIT: updated diagrams 05132018
Greetings Don!
This is a long one, and I ask you, respectfully, to bear with me. I believe your reading the following will be very useful to you, and many others who (also) learn from your postings...
The alternator wiring schematics you provided in the 7173Mustangs.com Tutorial are very nicely done. Very clear. I do, however, have two areas I would like to put forth for your consideration in making a few adjustments. I have attached an Enhanced version of your schematic pages. The enhancements are the same for all 3 pages. The first is self-evident, where I simply identified the "S" and "I" terminals on the Starter Relay, which "S" and "I" characters are often provided as raised letters on the molded Relay housing. I did take note that like myself, and some (not all) older schematics the Circuit "32" has a "32A" designation indicating something "different" about the otherwise same Circuit with respect to the function of the circuit segments. I found that kind of clarification to be useful.
The other enhancement is one that is lost upon a lot of folks as it was explained incorrectly by so many "experts" for many years. I only became aware of my having followed the "conventional thinking crowd" myself back when I was a young kid just learning about automobile repair. I was taking an Automotive Electrical Systems class, as part of the curriculum required for my A.S. in Automotive Repair Technology. The instructor was a former boxer by the name of Joe Renzi. He was a very likable gentleman who had many decades of electrical experience. When he began to cover the way the Ford Starting system worked he said, "Your book is wrong in one area, and I need all of you to pay close attention to what I about to tell you. You will find many mistaken ideas about auto repair in your lifetime, but this is a big one that will change everything you ever believed about electricity."
He then asked what the cranking voltage of the battery ought to be when testing the Cranking Circuit. I raised my hand and said, "We are looking for 200 - 250 amps on a V-8, with about 10.5 - 11.5 volts, but no less than 9.6 volts." "Close enough," Joe responded. "So, let me ask you this. In your book it says the Starter Relay supplies 12 volts to the Ignition Coil while the engine is cranking. Does everybody see that? Do you understand why?" I raised my hand, again, and said, "I sense a trick question here, but as I understand it the 12 volts is supplied to the coil to make certain the high voltage output of the coil is higher to help start the engine." "Yes," he said, "And that is precisely where the problem is. How do you get 12 volts to the coil while the engine is cranking over when the battery voltage has dropped below 12 volts? The bigger truth is the Starter Relay provides FULL BATTERY VOLTAGE - that much is true. But it is not 12 volts, as 12 volts does not exist during cranking. All you have is 11.5 volts at best for a small engine, and maybe as low at 9.6 volts on a larger engine. Even less with a battery that is not fully charged or worn down due to prolonged cranking."
Wow, he was right. Now it all made perfect sense. The normal running voltage of 10 volts, more or less, sent to the ignition coil is about what cranking voltage is. So, the ignition bypass to get battery voltage to the coil during cranking was nothing more than an attempt to get the voltage normally see when running, not to get 12 volts to the coil for better starting.
Ever since then I have been plagued with the knowledge that the oft quoted "Full 12 Volts" during cranking ignition bypass is entirely wrong. Usually it is something I find where I can't do much about it (a book or magazine). But, where I can share that insight I will, in conjunction with a heartfelt desire to not make anyone feel badly about being essentially hoodwinked for years with this one misunderstanding.
I share this with you for a few reasons. First, clearly you are respected and renowned member of the automotive repair field. Especially when it comes to Mustangs (and Shelbys). Second, with all the knowledge you clearly possess I feel you, of all people, will "get it" when I seek to reveal this tidbit to you. And I feel it is very unlikely you will be upset as you will be able to discern the spirit in which I share this with you. That said, I have enhanced your PDF file by first identifying the "S" and "I" terminals on the Starter Relay part of the schematics. And at the end of the "I" wiring in the schematic, I altered the explanation very slightly to provided more correct info re: what is being sent to the Ignition Coil, and even a brief explanation as to why that is the case.
I offer this in the spirit of one car guy who is always trying to learn more, and shares what he knows freely, to another car guy who has what I feel is a similar outlook on what his role is in our little community of enthusiasts and auto repair professionals. Please feel free to share this enhanced version, or a revision of your own reflecting this new and profound way of thinking, with others as you see fit and appropriate.
I will continue to look for more information from you in the future. It is a shame we live in areas so far apart from each other. I feel if we were residing in the same area we could become quite formidable, in a good way.
