I am thinking of adding a second cargo light to my Av and wiring a switch in the back to turn it on and off. If I wire it to the first light can I turn them both on and off from either location? Are these lights turned on by grounding and have power to them all the time? If I do wire them like I mentioned will the dash light go on even without the key on? I saw something about a resistor used on one setup, what for? I know there is a post about some of this but I just can't find it.