I installed 3 smart switches which are all on the same circuit in my house. I have never changed a light switch before, but I followed the directions very closely and watched a couple of Youtube videos to help me understand the different wires in the gang boxes. All the switches seem to be working (2 single pole switches and 1 3-way switch -- I haven't replaced the other 3-way switch). All of the switches have a light on the button. When I put my non-contact voltage tester near any of the switches, it beeps. Is this normal? Safe?

Edit: To be clear, the voltage tester doesn't respond to any of the other switches in my house, but of course those don't have lights or use the neutral wire.

1 Answer 1


ncv's will go off for just about anything. never trust an NCV with your life. cheaper ones will go off from shaking them.

i was in a house once where it went off in the entire upstairs. the house was also below large powerlines.

knob and tube , switch loops (where there is no neutral or ground) have a larger electric field. also a loose neutral could cause this.

check with a multimeter. place one contact one a "hot" screw and the other on the metal yoke or a ground wire. you should read a voltage. 0 is bad. 0 means the yoke isn't grounded and may carry a current.

I just checked and my NCV doesn't go off next to newer romex wired switches but does with the older switch looped switches. (klien ncvt-1).

my Commercial electric brand NCV will go off by rubbing it on my shirt. or when i put it back in my tool belt or when i walk around with it on in my pocket.

(ALso note that you only use a dimmer on one side of a 3way system)

  • Thanks for the suggestion. These particular smart switches don't have screw terminals, but individual wires for "line", "load", "neutral", and "ground", (and "traveller" wires in the case of the 3-way switch). I can't find a place to probe the circuits, since they're all insulated and connected under screw caps. Dec 6, 2020 at 17:53
  • 1
    @Quasi_Stomach if the ground is hooked up you are probably fine.
    – RadioSpace
    Dec 6, 2020 at 19:58

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