I'm glad to see that the wiring in my coach is just as confusing as yours. I'm annoyed that the negative wires are covered in red heat shrink tubing.
If you peel back the split flex tubing, you can see the color of the wire. It's most likely black. You are missing the second negative wire on the battery on the right. That is where the wire should go. That is if everything else is hooked up properly.
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