If the power cord is hooked up to the house or the genrator everything powers up fine, but without being plugged in (even with the engine running) nothing works.What could be wrng with it?

maybe your power inverter.

that one should have a change over switch that switches power supplies to it,on those it was usually a manual switch that should be located near the dash area,you have to switch that over for everything to work right,i own a 79 dodge tradesman motor home,and it has the switch to change it from generator to cable current,or house current off the plug or the cable,if u do not switch it nothing will work on it,they did this to keep from burning up the electrical system,if it fed two power supplies to the same power source it would fry the electrical system on it,good luck with it,also check at the input power supply on it,your switch may be located on the main panel for it,they put those in different places on different models,enjoy it l do mine.