Originally Posted by Pacostaco
At first I thought I was overloading the capacity but I used a volt meter on he incoming power and that is where the voltage was dropping
Just tapping into an existing 12v line is not sufficient to power a full size inverter. A: The wiring is not large enough to supply the high demands. B: It can cause a severe fire hazard if you attempt to do so.
I would start by going to the search box and entering "inverter install". There will be a number of threads addressing this issue.
From there, start a new thread and ask any questions that might still be unclear.