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I need help solving a mystery. A few months ago, I had an electrician install LED can lights in my son's bedroom. He completed the job with no issues, and it wasn't until a few days later that I noticed the problem. My son, sleeping in bed looking up at the ceiling, said "Daddy, the lights are still on." Sure enough, in the dark you could see that there was a very faint glow coming from the LED lights, even though the switch is in the off position. After a little experimentation, I figured out that this happens if the lights in the second bedroom are on. If those lights are off, there is no faint glow.

I'm figuring this is a wiring issue. I got in touch with the electrician but he was not helpful (essentially, "I don't know. Wasn't me."). If this can be fixed at the switch, then I can do it. Any ideas how this is possible and how to fix?

Here are all the details:

  • LED can lights getting residual electricity when switch is off, if lights in second room are on.
  • The switch is a Lutron dimmer with night light.
  • The wall switch used to control an outlet, there were no built-in lights in the room before. The electrician hijacked it to control the can lights that I had him put in.

Thanks in advance for any ideas or suggestions.

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    When the lights in the second room are off... does the night light in the switch also happen to turn off? – DeadChex Oct 7 '19 at 16:02
  • Hello, and welcome to Home Improvement. Interesting question; let's home someone here can help you. And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Oct 7 '19 at 16:30
  • I can't be sure that this is your issue but one thing I've seen with LED lights is that they take so little power to activate that just cross-coupling between parallel wires can induce enough current in the OFF string that they will light up dimly. – jwh20 Oct 7 '19 at 16:31
  • @DeadChex, the night light in the switch is always on. I.e., independent of lights in the second room. – Techmec Oct 7 '19 at 17:29
  • What type and quantity of bulbs are used in the second room? – JPhi1618 Oct 7 '19 at 17:45
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It's a Lutron dimmer with night light.

First, that should never have been used to control an outlet. You must not put dimmers on outlets, because if someone plugs in a non-lamp, the power-shaping issues can cause equipment to dramatically overheat and start a fire. If you have any more dimmers controlling receptacles, remove them now and fit standard switches with no powered features.

Dimmers and night-lights are both features that require power themselves to operate. Traditionally, powered switches like this got this power by leaking power through the light bulb. On an incandescent bulb, at very low currents they remain unlit - in fact they are practically a dead short until they start glowing. That is perfect for this.

However, LEDs actually put the power to good use - even small, defective power like this.

Pop out the switch and look for whether the switch takes a neutral wire. If it does not, this is a bad choice of switch. You need a more modern type, which requires neutral (I assume it's available there), powers itself between always-hot and neutral, and only sends power to the bulbs for lighting the bulbs.

The dimmer "clicking hard off", that is a feature of many dimmers, but here, it is a red herring. It still has a night light.

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  • We would need to see the switch wiring/model number to be sure. They come in different models and some use a neutral or ground to pass voltage through the locator light. Also, OP says this only happens when lights in the next room are on, which points more to a phantom type voltage. – JPhi1618 Oct 7 '19 at 17:45
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It has more to do with the dimmer that the other room lights. Solid State dimmers all have "leakage current" through them; there is no true "Off" unless the dimmer has an added contact in series that opens (provides an air gap). You can tell if yours has that because there is a further "click" you can feel if you push a little harder to the Off position. Assuming it doesn't, the amount of energy that leaks is very very small, so when you had incandescent bulbs they presented a high resistance to it and nothing would show up. But because the LEDs have a low impedance (resistance) solid state "driver" circuit, it can and does react to that leakage. The connection to the lights in the other room is that there might be some addition inductance across the wires run in parallel in your walls. That inductance alone would not show up, and maybe the leakage through the dimmer won't, but both together will.

So what can you do? You can live with it, you can get rid of the dimmer and use a plain switch, or you can replace that dimmer with one that has the "click off" at the end of travel.

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  • I believe you have this backwards. The incandescent bulbs present a LOW resistance to the current which is invisibly shunted through the bulb. The LEDs present a HIGH resistance which allows a high enough voltage to build up on the line which is enough to cause them to glow, albeit dimly. – jwh20 Oct 7 '19 at 17:16
  • With the picture OP has added, it does appear to be a "click off" type, which I would argue are much, much more common than a dimmer with no full-off. – JPhi1618 Oct 7 '19 at 17:31
  • @jwh20 and JRaef, thanks. I've uploaded a photo of the dimmer switch. As you can see, it's the kind that's a toggle with a slider to the side that's the dimmer level. So there should definitely be no current in the off position. Also, the glow most definitely happens when lights come on in the second room. The cross-coupling between parallel wires is an interesting hypothesis! I guess the only way to test/solve that is to go up in the attic and uncouple the wires? – Techmec Oct 7 '19 at 17:34
  • @Techmec, the wires in the attic will be stapled into place and should be covered with quite a bit of insulation. "uncoupling" them would be a challenge and at best you would only be able to partially separate them where they are accessible. – JPhi1618 Oct 7 '19 at 17:43
  • Of course you know this switch also has a night-light, so the dimmer "clicking hard off" doesn't make any difference - even clicked off, the night light is still lit. – Harper - Reinstate Monica Oct 7 '19 at 17:52

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