I am trying to install an outside motion sensor light. I have mounted the fixture to outside of house, ran all wires inside thru wall, and can't get it to work. there is a switch to the basement lights beneath where the wires come thru wall, but that switch is also connected to another switch at the top of the stairs, and both go on or off either way. is it possible to hook up the outside light to that switch as well, use a double switch to operate the basement lights and that light separately, or do i need to run a new line? the colors from the light switch to the basement are red, black, white and one bare, while the outside light only has white, black, and red. i really need help???

 

Welcome to the forums! The switches you refer to are 3 way switches, and there is probably not a neutral in the box. You need a neutral in order to operate this light. Where will you be deriving your power from? Not sure why your light has a red wire in it. Is that from the fixture or from the light box itself? Is there a more convenient location for you to put your switch, rather than where you suggested?

 

the wires i am speaking of are coming from the original light switch located in the basement. there is a second light switch at the top of the stairs with the same wires(one:red, black, white, and bare). i wanted to know if i could use the original switch that is in basement the wire & power my new outside light, or do i need a different power source? i will check to see if i can find another source, but for convenience i was trying to hook it up off of that switch, and maybe convert it to a double switch, but that didn't work lol, i was able to get the basement light to work but not the outside light, and when i got both to work they both stayed on, lol.

 

As stated by Chandler you may not have a power source. Not all switch boxes have a neutral and just because a wire is white does not necessarily mean it is a neutral. No neutral, no power source.

Do either of the boxes have a 2-conductor cable (black, white, bare)? If so you need to write down how it is connected, disconnect it, and measure the voltage between the black and white wire using either a multimeter or a test light but not a non-contact or pen tester.