I opened up my old inverter, the one that I took out of the RV.
It turns out that inside of the old inverter, the BLACK battery negative is connected with a BIG shunt, to the GREEN chassis ground cable lug. For the new inverter, I added an outside cable to connect NEGATIVE to GROUND (12v, not grounding any 115v). (to accomplish the same thing as the shunt insidet he old Trace inverter)
After that, everything seems to be back to how the RV was before.
Thanks a lot guys for keeping me positive and giving some food for thought.
