Hello,

Any guidance on how to replace/install an old 4 wire light switch (2 black wires, one red wire and one green wire) with a new three wire motion-detection light switch (2 black wires and one green wire)?

I'm confused and the instructions do not give any help.

Thanks!

old 4 wire light switch (2 black wires, one red wire and one green wire)

That sounds like a 3-way switch. 3-way switches always work in pairs.
Is there another switch for this light?


motion-detection light switch (2 black wires and one green wire)

All motion detectors I have seen have 3 wires, a black, white and red, not counting the green.
We don't usually count the green or bare wire.
When we say 2 or 3 wire, we really mean 2 or 3 conductor. The green or bare is the ground and is not a conductor. Therefore, when we say 2 wire we really mean 2 conductor with ground which of course is 3 physical wires. Confused?

Can you post the instructions that came with new switch?

That sounds like a 3-way switch. 3-way switches always work in pairs.
Is there another switch for this light? Yes, there are 2 switches total. They both turn on the same light.



All motion detectors I have seen have 3 wires, a black, white and red, not counting the green.
We don't usually count the green or bare wire.
When we say 2 or 3 wire, we really mean 2 or 3 conductor. The green or bare is the ground and is not a conductor. Therefore, when we say 2 wire we really mean 2 conductor with ground which of course is 3 physical wires. Confused? Kind of confused! lol These motion detector switches have the two black wires and one green wire. (No red and no bare wire).

Can you post the instructions that came with new switch? The instructions do not tell anything more than the obvious, connect black to black, and green to green. :mad:

Thanks for your help!

If there is only two blacks the motion detector is operating without a neutral. It is just an automated 2 pole or on/off switch. It will not operate properly in conjunction with the other 3-way switch.
If you connect one of the blacks of the motion switch to the wire that was on the common screw of the switch you took out, and the other black to one of the other wires it will work. But only with the other 3-way switch in one position. It will not function with the 3-way in the other position.

If there is only two blacks the motion detector is operating without a neutral. It is just an automated 2 pole or on/off switch. It will not operate properly in conjunction with the other 3-way switch.
If you connect one of the blacks of the motion switch to the wire that was on the common screw of the switch you took out, and the other black to one of the other wires it will work. But only with the other 3-way switch in one position. It will not function with the 3-way in the other position.

Thanks young man! I'll try that! :p If my house is still standing tomorrow, I'll know I did it right, eh? Lol

Have a great day!