I used incorrect nomenclature in a couple places, and I made a couple assumptions that are not wise assumptions to make. Original answer is below, corrections here. I'm thinking the question title should probably remain unchanged (mods?).

My specific wiring situation is called a switched loop. There is no neutral wire in a switched loop. They are "Always-hot" and "Switched-hot"

I'm disappointed there's no UL-listed way to accomplish my original intent--but no more disappointed than I'd be to arrive home and find a fire truck on my lawn. Thanks to JACK (and especially Harper) for the corrections and alternate ideas. I'll answer this myself once I decide on and implement a solution. It's no emergency, so this may be awhile.


I want a (110v) pilot light to indicate my closet light has been left on.

The switch box has only a single of each: hot, neutral, ground--no wirenuts--so it's downstream. Therefore it seems anything I connect in this box will be wired in series to the light. Is there a way around this?


I stole this image from Joe. It's nearly perfect, but IIRC the lamp fixture also had a ground terminator.

light switch downstream from light

I want the pilot in the (single gang) wall plate as found in a review of this item, which I've purchased.

110v switch with small, integrated, aftermarket pilot light

This little LED has only 26-gauge wire, likely making a series connection an unwise overload risk. Heat shrink conceals something on one of the leads, and I don't know what it's for. I suspect it regulates the AC current for directional flow--do LEDs require this?

small 110v LED with heatshrink-wrapped wire

I've already mounted the LED in a plate, but my final solution doesn't necessarily require this specific LED. I do like the small size and its brightness.

I have several larger, red ones that are not this specific item but look the same to me. I could use one of them if necessary.

large 110v red LED

My red LED has 18 gauge wire, so I tried wiring one in series. But the closet light only flickered (far slower than 60-cycles) while the LED indicator turned on. The housing is easily spacious enough to contain whatever is lurking in the other's heat shrink. So maybe my directional current hunch is correct, and certain components in each light (indicator and fixture) conflicted, resulting in the flicker.

Both LEDs light up when I just stick them in an outlet, so I assume there's no malfunction with either one.

Finally, I'd rather this look good when finished; it's in my master BR. While Decora is preferable, I can settle for the traditional style toggle. I'd prefer to avoid an industrial-looking switch:

functional-but-unattractive illuminated switch


My closet light switch is outside the closet, and when I'm in a hurry I tend to close the door without remembering to turn off the light. It's easy to miss until returning at night when the light is visible under the door.

Lately that's happening more frequently, and it's stressful coming home to learn I've wasted ten hours of electricity. The closet light is an LED, so this is more for principles of efficiency, conservation, and peace of mind than actual money loss.

The closet light is an LED (not incandescent), so it's probably inadvisable to "cheat" and repurpose the ground as neutral--but I'm open to suggestions from someone smarter than I am. The walls and ceiling are finished, so pulling wire would be enough hassle to cancel the project--I'd rather install a pull-chain switch inside the closet and replace the existing wall switch with an in-series jewel light.

I initially sought a manufactured solution, but I'm flummoxed by how many "nightlight" variants are available and yet I can't find a wire-and-go switch where the indicator turns on while the load is powered, even aside the series vs. parallel concern.

I'm confident if both the closet and pilot lights were incandescent they'd work in series--but that seems a step backward after upgrading to more efficient LEDs. Then again, leaving an LED on long enough spends as much money as an incandescent that's always noticeable enough to turn back off when I'm done. :,/

Several DIY SE questions look very similar but differ, with this one being the closest I've found--his intent similiar to mine. My initial thought of using a double-pole switch was mistaken--as I'm still downstream from the light--so I'm struggling to conceive a non-series connection.

There's probably enough room in the junction box for a small transformer; if I give up on 110v I might search for a DC LED with a small power supply, rigging that instead. Of course I'd first leave it plugged in somewhere for a week to ensure it wouldn't overheat. That seems to be the very-long-way-around solution, but I suppose it'd work. I expect it would also draw more current than the other solutions, negating its own benefit.

Seems like this should've been a ten-minute-trip-to-Lowes solution, and I've already killed a million brain cells over it. Thanks in advance for any guidance here.

  • Have you considered a motion sensor switch? – JACK Oct 19 '20 at 19:10
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    @ThreePhaseEel: This is in the corner of my house, where the attic is ~6" high. It no doubt could be done...however this has already consumed far more of my time than I'll ever recover in electricity savings. Fishing wire through finished walls while lying prone on insulation, arms outstretched--looking conspicuously NOT like Superman--here's where I concede defeat. – zedmelon Oct 20 '20 at 16:38
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    @JACK, I wanted to mention... your bio is kickass. You've led an interesting life, thanks for posting that. – zedmelon Oct 20 '20 at 16:51
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    I most certainly get where you're coming from. I know I've seen standard, old-school toggle switches that light up when on. However, all they seem to sell these days is ones that light up when off (for example). Have you considered one of those? I accidentally installed one in our bedroom (didn't realize it had the light-up feature when I bought it) and we very quickly learned to ignore the glow at night. – FreeMan Oct 20 '20 at 17:18
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    @FreeMan: Nah. Theoretically growing comfortable with the light on would mean I'd notice something amiss with the light off. Yet I've experienced alarm fatigue in a NOC where Nagios was (over|mis)configured for months until someone cleaned it up. Seeing all those green statuses was wonderful, but it was awhile before we were able to once again take alarms seriously. A negative alarm would be guaranteed to affect me worse than that gig did. (PS: thanks for the validation--I actually have one purchased years ago at Lowes in my basement, so I know they exist) – zedmelon Oct 20 '20 at 20:41

Your wiring configuration is an old style switch loop, which does not provide neutral.

To stop killing brain cells, stop violating Code. Any solution that violates Code, cross it off immediately: kill it with fire before it kills you with fire. All that stuff you saw in Amazon reviews and Youtube videos are jackasses trying to burn their house down (plus, they weren't on a switch loop like you are).

Also, everything you use must be UL-Listed as equipment for AC mains use in houses. Not RU-Recognized as components. Especially, no using random bits you got off Alibaba (Amazon Marketplace is basically Alibaba, so is eBay, Banggood etc.)

You want this instead

enter image description here

Get a 5-10 minute one, and get one with a "hold on indefinitely" position if you want that. You can use the electronic push button variety if you find one that does not need neutral (they are out there).

A commercial pilot light is right out

The problem is, they all need neutral, and you don't have it on a switch loop.

The Hail Mary play: low voltage DC/AC

It is perfectly allowable to attach a UL-Listed low voltage power supply to a light, if the light provides a legal wiring method to do that. For instance many companies make 24 VAC transformers that go in a common round knockout. From there you qualify for the very much relaxed low voltage rules in NEC. Now you can use /2 thermostat wire to carry 24VAC or other voltage to wherever you see fit to have any kind of an indicator.

There is one gotcha: you cannot intermix or commingle low voltage wires with AC mains wires. You will note any of the knockout-mounted transformers will provide for the low voltage to be outside the knockout. So what is Right Out is to install a low-voltage LED inside the AC junction box.

Or just go LVDC for the whole kaboodle

Honestly, given the low power requirements of LED lighting and the ready availability of 12/24 VDC LEDs, there's no reason not to just make the entire lighting branch low voltage — the closet light, the switch leg, the switch and the indicator.

You need a UL listed power supply in the closet, but after that, you have a great deal of latitude. (but still not Alibaba).

There is one snag: most consumer switches are not UL-listed for any DC voltage.

But here's a wacky idea: use an AC low voltage supply, and use diodes to treat the switch loop as two completely separate loops. Positive flow, the pilot light is shorted around (by a diode) and the switch is in series with the lighting LED. Negative flow, the lighting LED is shorted around (by a diode) and the switch is in series with the pilot light. Add a little capacitance to arrest flicker on the pilot; many DC LEDs already have that built in.

You can reuse the /2+gnd Romex cable for low voltage power, as long as you have partitions inside the junction boxes. Using wire and cable for low voltage that was intended dor AC mains wiring is fine. It would be a Code violation to use safety ground for ordinary operating current, though.

  • Why didn't I think of that??? Oh, it's Monday.... better than a motion sensor.+1 – JACK Oct 19 '20 at 20:06
  • [The problem is, they all need neutral] I was hoping that wasn't the case--dang. I was wondering if that was a true neutral (should've listened to that hunch more). So then what's the term for the non-hot wire in a switch loop? – zedmelon Oct 19 '20 at 22:21
  • I'd hoped I was merely searching the wrong Alibaba pages, and someone makes a lighted switch that can do on or off (bypassing all of my brain damage). LVDC and the timer are both good ideas; thank you. – zedmelon Oct 19 '20 at 22:34
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    @zedmelon The 2 wires in a switch loop are "Always-hot" and "Switched-hot". If neutral is not present, white must be always-hot. Alibaba is another brain-cell killer. Remember NEC 110.2, everything must be approved which means UL-Listed. Nothing from Alibaba is, it is pointless to shop there. Anything AC mains must be gotten from Home Depot, ACE, City Electric, etc. – Harper - Reinstate Monica Oct 20 '20 at 2:06
  • Harper, thanks so much for taking the time for a detailed answer. And again for the supplemental edgjyimickayshin. Truly appreciated. Still deciding on an approach but will update with the result. – zedmelon Oct 20 '20 at 16:41

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