I've never seen an in dash RV radio without an inline fuse, not that they don't exist, but I aint seen one yet. Check the connection at the radio for 12v DC if you have it then it could be an internal fuse or fuse link. If no power there, work your way back to the power source of the unit. When you come to the first connection check for power there. Repeat until you find power, your bad connection or fuse.