Join Date: Aug 2006
Location: Arlington, VA
Thanked 14 Times in 12 Posts
Rep Power: 12
Although one wire runs from one thing to another, they're no doubt wired in parallel, not series. There must be another wire for the return.
Figure the total possible draw for all items and install a fuse which is about 25% more than the highest possible draw.
Be absolutely sure not to use the cigarette lighter plug for anything substantial. Your AWG16 wire is none too large.