I am stepping out on kid of thin Ice, I am not an Expert, I just have been really searching and figuring out what I need.
And talking with Mark at MAD Electronics for quite some time a few months ago, I asked him the Same Question - Why is that Wire a 12 Ga. that runs from the Ignition Switch all the way for my Car to the Starter Solenoid ? He explained to me how GM designed their Electrical systems and some of the design does not make sense with today’s parts and systems.
The Ford Style Starter Solenoid was a better way of managing the Hi Amp switch Remotely with a lower Amp/ Gauge wire – Sorry I had to admit that
It’s like 12 - 15’ or more on my car with the Console - That is why, it’s a "Too long of a run" and does carry a lot of Amperage, which I also tried to get a Value for How much Amperage Runs thru this Purple Wire just to Close the Cranking Circuit ?
I came up with about 30 – 35 Amps (Do not know if this is accurate) but I figured I would Not try and go down on the Wire Diameter and chance a problem.
This is Not the Starter/ Battery Cable side we are talking about, this is the “S” side of the Starter Solenoid.
Also, the “Flat Wire group” I know it as the Harmonica Connector is labeled “Directional Signal Switch Connector” on your Wiring Diagram and is Not a part if the Ignition/ Starting system, those wires are Turn, Brake and so on.
The Ignition Switch has a large 12 Ga. Red supplying current from the Bus Bar on the Horn Relay thru the Firewall Harness disconnect to the Ignition Switch, out is the Pink 12 Ga. To supply Power to the Fuse Box and the Purple 12 Ga. that runs thru the Neutral Safety Switch and then to the “S” Post on the Starter Solenoid.
Pic of my Harmonica Connector - None of this is for the Starting Circuit. The 14 Ga. Purple coming out is for the 4 Way Hazard Flasher supply.