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Edit:

I have confirmed that my main question is answered in another post. But there are still things that bother me.

  1. Why is there a buzzing sound when the bulbs work?

  2. The new bulbs do not light up in another bathroom with the same kind of dimmer switch. Why is that?

I understand these questions are tough nuts to crack without certain details that might be hard to obtain. For example, it might be hard for me to dismantle the existing switches and look under the cover or to know the brand/model of the switch.


I just replaced my bathroom light fixture bulbs with newly bought bulbs (LED, A19, 40W equivalents). What I get is a head-scratcher: the bulbs light up dimly as soon as I screw them on and the switch is off. If I push the switch on, the bulbs function normally, but with a noticeable buzzing sound. Looks like this:

enter image description here

I am trying to figure out if there is something wrong with the new bulbs or the circuit. This is the box that the new bulbs came in.

My previous bulbs are of the same brand and the same kind (LED) but a higher wattage. My money is on that this has something to do with the switch. Most of my switches have a dimmer and a little LED that helps locate the switch in the dark. Does this mean I will have to go back to my old bulbs? Do I need to worry about the circuit?

  • 1 - "same brand but a higher wattage" - same type (i.e., LED) or just same brand (Ecosmart)? 2 - Does your switch have any of: "glowing light in switch when off as a night light", "dimmer", "timer"? – manassehkatz-Moving 2 Codidact Dec 2 '19 at 1:28
  • @manassehkatz-ReinstateMonica Thank you for such a swift response! I am still editing the question. For some reason uploading pictures is giving me a headache. – Eddie Kal Dec 2 '19 at 1:29
  • @manassehkatz-ReinstateMonica Yes,the same type and brand; the switch has an LED indicator thingy and a dimmer. – Eddie Kal Dec 2 '19 at 1:37
  • See proposed duplicate. If your dimmer switch doesn't have a connection to neutral, then it uses the load wire as effectively the neutral, which sends current through the bulb. An incandescent bulb won't light up, but an LED can manage at least a little bit of light with very little current. For what it's worth, I have used Lutron Diva CL dimmer switches with LED bulbs and fixtures with great success. Unfortunately, they don't have the nightlight, but they do have a pot to adjust the dimming range, to match the dimmer with the LED – Peter Duniho Dec 2 '19 at 2:08
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    It sounds like your dimmer is not designed for LED bulbs. There can be a considerable range of voltage tolerances for incandescent-only dimmers, and the buzzing comes from the way the dimmer truncates the voltage waveform and the effect of that on the bulb's internal power conversion. A better dimmer specifically designed for use with LED bulbs will likely make all of these problems go away. – Peter Duniho Dec 2 '19 at 3:17
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The first problem is probably the dimmer, you need a smart dimmer (they usually require a neutral) some lighted switches use neon lights in the switch, even these draw enough to light many types of LED lamps. There are some dimmers that are LED compatible that do not require a neutral. You need to find an LED compatible switch and everything will work the way it should.

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  • The box says NON-DIMMABLE.
  • You have a dimmer.

LEDs are different from incandescents.

With incandescent bulbs, you can leak a little current through a light and it doesn't matter. You can vary the current and it works fine.

With LED bulbs, a little current goes a long way. So a very tiny bit of current leaked through by a dimmer "nearly off" or for indicator lights/electronics to work when "off" is enough to cause a glow or blinking lights. A larger current in "dim" mode can cause blinking, buzzing or other problems.

Why is there a buzzing sound when the bulbs work?

Many dimmers work by, essentially, turning the power on/off very quickly. With an incandescent bulb that works great - "all the power 1/2 the time" is basically the same as "1/2 the power all the time" - i.e., 1/2 as much light. With an LED bulb, special circuitry is needed to figure out that "all the power 1/2 the time" means "1/2 the light" and not "turn the light on/off every time the power goes on/off. Depending on the circuitry, a non-dimmable LED bulb can react by:

  • Turning on/off a lot == blinking
  • Not working at all
  • Buzzing as various components that were not designed to turn on/off very quickly end up turning some of that energy into vibrations.

Return the bulbs and get ones that are marked DIMMABLE.

  • Oh I see. Since I have never worried about the dimmer or used it, I thought I could just leave it at max and it would be like an ordinary wire (unnoticeable resistance). Am I totally mistaken in thinking this? Also dimmable bulbs are decidedly pricier... – Eddie Kal Dec 2 '19 at 1:47
  • A dimmer can be "simply on" when at max. But that is not necessarily the case. If you really don't use the dimmer (not sure why anyone would in a bathroom), you could replace it with an ordinary switch. – manassehkatz-Moving 2 Codidact Dec 2 '19 at 2:52

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