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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.

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.