Converter problems

I have a 2008 Rockwood Roo 23SS. It has a Paralax power supply 7100 converter in it. I have no 12 volt power. The Battery is dead and not charging even when plugged into household current. I found a diagnostic table online for the converter. I followed it and it says the converter is ok but may be in an over current state a bad battery or bad battery wiring. It talks about pulling fuses to determine where the problem is. I pulled the fuse but then what am I supposed to check to see if that circuit is the problem. It says there may be a short. If there were a short shouldn't the fuse be blown? Also my 12 volt circuits don't work even when plugged in. I am thinking I may have a bad battery and this system used the battery as a buffer? Any help is welcome.