12V RV Fuse Box - Vintage Trailer Supply This is the highest quality stand-alone RV fuse box we've ever seen. It is a surface-mount box that allows for wiring up to 9 independently fused DC circuits. It's ideal for replacing a converter that contains an internal fuse panel (like older Univolts) with a converter/charger that does not (like modern Inteli-Power Converters). 12 volt fuse box? - RepairingYesterdaysTrailers - Tapatalk No idea what you may run into on a fifty year old trailer. I usually "prepare for the worse case", that way I won't be surprised what I find. If you can't find a 12 volt fuse box, then you will need to trace the power source from the battery to the switch/light(s).