I meant a wiring diagram of the add-on work, not the original stuff.

Ohhh, all good now, it was as I thought, I connected the extra ground and the amp stopped doing it, and the car starts every time now so far, and the DIC still remembers what it was set to before, so I think I am good to go, it had to be the older battery..

Good to go for sure, and back to the way it was, I can now use my remote start again.
And I am not worried about being stranded, or having to play with the batt ground for the car to start.
Thanks guys.

Great news!

Thanks for letting us know how it turned out!

Well, occasionally I still see the charging system error come back when the bass hits hard, and the volume is up pretty high, never had issues before as I tuned the amp gain to not clip at the max vol I turn it to.
I see the DIC show the batt voltage drop to 12v once and a while, and at times I see it peak at 15v..
No starting issues anymore though.

I am thinking maybe the voltage regulator, I'll test it when I can, another 60hr week...
I also notice sometime the voltage sounds like it drops when I turn the wheel, only occasionally though, the ac and all sounds like it slows down, then comes back up to speed...
The belt feels tight, it is in good shape...
Man I hate gremlins!

The alternator can't keep up 100% with heavy voltage fluctuations. The battery (or batteries in your case) do that. If the engine (therefore alternator) is running somewhat above idle, it will have a better chance of keeping up with rapid fluctuations.

I noticed something else, it seems the voltage was showing as 15.0-15.5v on the DIC when the bass hits and the error shows, that is a tad high right?

I know this is one of the most aggravating issues I have had in a while, I really do not want to spend another 450.00 on a high power alt...

Can you monitor the current the amp is pulling so you can see if it'* a supply issue causing it.

What carfixer007 said ^^^^^^^

. . . and:

Yeah, that'* high. Maybe the regulator isn't as fast as necessary dropping down from high output? Long stretch there but I can see how that'* possible.

I'd be curious what a real gauge says compared to the DIC.

I will try to see what it is actually pulling, I know its specs though.
https://rockfordfosgate.com/products/details/r750-1d/

40A average, 80A max

I do run another Amp for my 6x9'*.
https://rockfordfosgate.com/products/details/p300x2/
23A average, 45A max

I doubt both hit max often, but when they did before this issue I never had any issues, but of course I ran 2 batteries..
And to be safe that is why I bought a better alternator.
Their suggested alt for each amp is 75A alt...