6 volts or 12? Tail lights on a 12V system work well with 18 Ga. wire. For 6V I'd go up a size or two, probably 16 Ga. or possibly 14. I've always had a habit of using one wire gauge above minimum for all circuits, as there's very little cost difference on the initial installation, and "voltage drop is forever"! Be sure to use fuses capable of protecting the wire, not nece3ssarily the end item in the circuit. For instance, 18 Ga. wire needs a 7A. fuse max, 16 can carry 12 A. safely, 14 gets a 15 A. or maybe 20, and 12 Ga. can handle 25 amps or a little more. As the wire gauge number gets smaller, the diameter of the wire and its current capacity increases.
If you're going to wire two tail lights and maybe a license plate wire from the same conductor headed toward the rear, use a 14 Ga. wire. It can carry 3 or 4 tail light sized bulbs easily. use a 10 or 15A. fuse.
Jerry
