Stop in for a cup of coffee

If I'm right, the fix could be as easy as moving the wire from the main splice to the other ammeter stud.
The loose wire could be spliced in,
View attachment 1715450484

or given a ring terminal if its long enough.
View attachment 1715450492

Thanks, I saved the diagrams if we need them... If he hasn't gotten it fixed yet, I can help him...