Low charge to no charge issue pulling hair out

I did that and looked at the entire loop from battery termal wire all the way to the ammeter and bulkhead both sides no wire issues or connector issues everything clean tight
Did you test for voltage drop under load at every point of connection?

If you have a wire with 15 strands in it
The load is shared by each strand.

Now let's say you have the same 15 strands but 14 of them are broken.

Now all the load has to be carried by the one strand.

Both the first and second example will show the same resistance on an ohm meter. But under a 5-10 amp load the first example will have a 0.08v voltage drop. But the second will have a 1-2v voltage drop.


The single strand under load increases in resistance.


Thing about an interstate with 4 lanes all the cars can pass past a point on the side of the road at full speed

This is all 15 strands working correctly


Now block off 3 lanes and the traffic crawls.

This is with 14 of 15 strands broken



If it's late at night and there is only one car for miles that car can pass that point at full speed regardless if it has 4 lanes or 1

This is how your ohm meter works.