u have to have 3 wires hooked up for this to work. red yellow and black. blk is ground. yellow is constant power (like off the batt) red is switched power (turns on with ign) you can wire the red to a switched source or use a switch and u will retain all memory settings-
i would run a new run. but if that is absolutly out of the question id use a in line fuse holder. the rings and a bolt should work, but is kind of ghetto imo