I have a home built in 1950 and a laundry room added sometime in the unknown future. There is a light switch that seems to be emitting electricity according to my Fluke voltage tester. I noticed it while replacing the switch. When I move the tester anywhere within an inch of the box, even without touching anything, it detects voltage. The two gang box is metal and the wiring looks like it's been there at least a decade. It does not appear to be grounded.

I have never been shocked by the light switch but am concerned. Why is it doing this? Is it unsafe? How do you fix it?

Light switch leaking electricity

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2 Answers 2


This is a non-contact voltage tester. It's not telling you there there is current passing through the wires, just that AC voltage exists. Since you switch the hot connection within a light switch, there will always be voltage present around a switch (unless you have tripped the breaker). It's the wiring after the switch where you shouldn't see voltage with a non-contact tester. If you do, then someone may have miswired the switch and switched the neutrals.

  • Okay, that makes sense. It seems unusual that this is the only box in the house that has non-contact detectable voltage. Oct 30, 2013 at 19:23
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    @Jason I'm not sure why voltages in other boxes can't be detected, but if you (carefully) open up another box and (carefully) wave the voltage detector around near the wires, I guarantee it will go off. Which it should. Oct 30, 2013 at 19:50
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    The only thing to check is if they wired the ground screw on the switch to the hot instead of the bare ground wire. Otherwise, something as simple as the way the wire was coiled in the back of the box may affect the range of the non-contact tester.
    – BMitch
    Oct 30, 2013 at 20:12
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    I would definitely check to make sure there isn't a voltage on the metal box. Oct 30, 2013 at 21:12

also those NON-contact voltage detectors are all different, even identical model/brand. i've always found that alot of them detect voltage from 1-inch and greater distances. i've gotten lucky with a pair of Klien ones that won't detect until your actually touching the wires insulation. i recently bought a really nice looking one with a vibration motor and a nice bright LED, but it detects voltage from almost 6inches away on a 110v source. from a diagnostic standpoint, they are useless if this sensitive.

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