Every Garmin I've ever used will take 12v input through the power cord, they are designed that way.
I'm not exactly clear on what you are referring to by "bare wire cord" but if you are using 12v you need to use the 4-pin plug in the back of the unit.
https://buy.garmin.com/shop/shop.do?pID=519 (you can find it cheaper elsewhere)
Make sure you use red & black and not the signal wires or you'll fry your unit. The fuse should not be more then a fast acting 2Amp.
