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I need to install a new motion detector light switch. My old motion detector switch only had 3 wires (hot, neutral and ground). I only have 2 wires in the wall a hot and a neutral wire. The wall is already grounded. The new motion detector came with hot, load, neutral and ground. Can I still use this motion detector with only two wires (hot and neutral)? What do I do with the ground and load wires? Thanks for your help. Val

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    This is very confusing. You say you have hot and neutral wires in a switch box but a switch cannot work without a load wire. Perhaps you meant you have hot and load but not a neutral wire. In this case, no, you cannot use that switch. – DoxyLover Oct 9 '17 at 17:34
  • Ok if we just use a regular light switch that you turn on with flipping the switch we only have a hot wire and a neutral wire that connects to it. We don’t have a load wire. – Val Oct 9 '17 at 17:55
  • Should be an answer doxylover.+ – Ed Beal Oct 9 '17 at 17:56
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    Val , what you have is a switch leg, a hot then the switched line returning to the light. The white should have been marked with another color, this is very common. Newer code requires the neutral but not before the 2014 code. – Ed Beal Oct 9 '17 at 17:58
  • We have a 12-3 wire. We have a Red, white and a black. The Red and black wires have power the white wire have no power. – Val Oct 9 '17 at 18:12
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The new motion detector came with hot, load, neutral and ground. Can I still use this motion detector with only two wires (hot and neutral)?

No.

As Ed Beal commented, you likely have a switch-loop where the apparent "neutral" is really a switched live.

It may be the old switch drew power parasitically through old-style incandescent tungsten-filament light bulbs. This is the sort of arrangement that often doesn't work well with LED bulbs and can cause odd effects including flickering.

If your new switch came with instructions - and they all should - you can check there if it is capable of working with a switch-loop. I suspect this is unlikely.

If so, the only way to use your new switch may be to open up the wall and replace the wiring with 4-core cable to bring a real neutral and a ground into the switch box. You'll need to follow local codes and probably pick an established switching scheme to avoid tripping your current or future GFCIs (or RCDs etc)

The wall is already grounded.

I'm not sure what that means. Most modern electrical codes require grounding of any exposed metal parts and metal backboxes etc. Unless you have a metal wall, it isn't a thing that would be grounded.

If you mean a metal back-box in the wall is grounded using the metal sheathing of the power cable, that would make sense. You could then connect that ground to your switch using a pigtail.

You still need a real neutral.

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