When we plug our 2001 Shasta 5th wheel into house current only the microwave and A/C work. None of the 12V lights work. When we plug into the truck the 12V items do work. We have never used the camper battery and it's not in the camper. Seems as though the converter is not converting the household current to 12V. Could a fuse behind the mail rocker in the converter box be blown? Would that cause the problem? We don't know what to look for. Could someone please help us out with what could cause this problem?