enter image description here

I wanted to replace a light switch in my 70s built house with a motion sensor. The motion sensor has 4 wires: two black one green and a ground. When I unhooked the old switch I found it was connected to two wires. The top was straight forwarded but the bottom is a continuous wire looped around the screw.enter image description here

I tried to connect a black to the cut wire and everything else to the continuous wire. The lights came on when I flipped the breaker but the switch didn’t work, ie. Wouldn’t turn off.

I figured I should understand what’s happening before any more experimentation. The local hardware guys were stumped. They just said the older house around here have some very janky electric!

Any help much appreciated.

Thanks all for the info.

Yes it appears the the continuous wire connects all three switches. Photos below.

Unfortunately the instructions are pretty useless, it just says connect the two blacks to two blacks from the wall, and the green and ground to ground wire from the wall. Also photo'd below.

It's a Lutron and does appear to be a UL device, at least it has the logo on the box.

@phil-g thanks much. I dont know anything about electric. Would you say to connect the blacks to the two grey wires (the cut and continuous) and try to attach the green and ground to say, the metal box? Or is there an identifiable ground wire?

Thanks again!

enter image description here enter image description here enter image description here

  • I like the word "janky" - it certainly applies here! Is this part of a 3-way switch set up? The way that's wired around there, I'd think they used the continuous wire as a traveler. – FreeMan Nov 7 '19 at 21:24
  • 1
    Is this a UL listed switch? I haven’t seen a green and a bare wire ground on a UL listed switch. You may need a neutral but reading the instructions should provide that , some cheap overseas stuff is not suitable for use in North America. – Ed Beal Nov 7 '19 at 22:34
  • @EdBeal -- the double ground is a thing on some Lutron units – ThreePhaseEel Nov 8 '19 at 0:50
  • What make and model is this motion sensor? Also, can you post a photo looking more squarely into the back of the box? – ThreePhaseEel Nov 8 '19 at 0:50
  • In your last photo, you can just barely see a bare copper wire in the back of the box—that’s your ground, which should be connected to the two grounds coming from your new switch. (It should already be connected to the box and to all other ground wires in the box, but if it isn’t, you should do that, too.) – prl Nov 10 '19 at 16:40

The looped through wire will be the live feed, and it continues on to power another circuit, probably the other switch.

Motion sensors usually require power of their own to function, and in newer installations there'd be a neutral available to provide that circuit - as there appears to be in your box. Check the instructions that came with the sensor as to the wiring but this looks like most of the dimmers and sensors, the green wire provides the circuit by connecting to the ground along with the bare wire. Not exactly per code, but that's how they've been sold for years.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.