As it says on the tin, I just installed my new switch, and it seems to work just fine (both switches function as expected - the wiring/setup was identical between the old & new switches), but (thankfully), before I touched the switch after turning the power back on, I ran my AC voltage detector across them, and surprisingly there was voltage detected.

I thought maybe this is normal, but after checking all of my other switches, no voltage was detected in them. So now I'm afraid to touch the new switch!

The condo is an older building (built in '63) and has no grounding wire; I made sure to mount the switch to the metal box first before testing, as I assume it grounds itself to its box. Any experts here that can advise?

Here's a link to a photo of the old wiring pre-installation, and the new switch showing current on the buttons: https://photos.app.goo.gl/weTS8YD2wdm3tqVm7

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    Are the other switches double? Where they on or off when tested? You're picking up the electric field. that's common, don't worry, you're detecting voltage, not current. – JACK Jul 19 '20 at 0:35
  • Yes, there's a second bathroom with the exact same setup. There is no current shown on those switch buttons (nor on the old switch buttons of this switch - only this new one). *Edit: They were on and off - tested both ways to be sure. – David Vasquez Jul 19 '20 at 0:39
  • how are you measuring current? – jsotola Jul 19 '20 at 1:38
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    @jsotola I think OP merely misspoke. I edited to reflect likely intent. Lots of people toss in “current” when they mean “voltage”; which is like tossing in “height” when you mean “width”. – Harper - Reinstate Monica Jul 19 '20 at 18:26
  • @jsotola, You are correct, I'm a layman, not well-educated in this, just doing some basic home upgrades and trying to stay safe doing them. To those of you who suggested phantom voltage (@JACK, you were the first), you were correct. The switch has proven safe and all is well. Thank you for reassuring me! – David Vasquez Jul 20 '20 at 17:45

I know that seems worrisome, but don't be alarmed. The non-contact voltage testers are notorious for giving false positives. They are overly sensitive. A better way to use one is to hold your finger on the opposite side of the tip of the ncv tester whenever you hold it against a wire (or in this case, a switch). This will help to deaden the sensitivity, but will still indicate a truly live wire conductor.

Your switches are plastic and should also prevent shock. enter image description hereenter image description here


Well you can have phantom voltage but since you did not mention the measurement method I would say this is normal! The lights work but sometimes a live wire is detected on a neutral or even a ground. This is called phantom voltage and can be found in almost every installation.

  • a neutral or ground detecting as live is not normal. it's just that those non contact voltage detectors are hard to aim. a switched wire sometimes dertecting as live is normal, an appliance or control detecting as live is normal. – Jasen Jul 19 '20 at 1:20
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    As a professional electrician I can tell you a neutral will turn a non contact voltage detector and will knock you on your butt if you get your body in the path first this is totally normal in an energized circuit next this is why both hot conductors in a multi wire branch circuit have handle ties so you won’t get shocked! Depending on boot leg grounds quite common all 3 may carry enough to light a non contact detector. – Ed Beal Jul 19 '20 at 6:27
  • I've never seen more than 10V on a neutral – Jasen Jul 19 '20 at 6:44
  • @Jason you have very limited experience then. I have seen more that on the ground very common with heavily imbalanced loads – Ed Beal Jul 19 '20 at 15:51

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