[Shane826]

Your converter is not convertering 120VAC to 12VDC which means shore power is unable to power those 12VDC systems (lights, fans, radio, toilet, etc) or charge the battery. Once the battery is gone you have no 12VDC power to run those systems. When you plug into the truck you are introducing an outside 12VDC power source, which powers those systems. You need a new converter/charger unit.