# 3-way CFLs How do they work? **URL:** \ **Category:** Factual Questions\ **Created:** [October 20, 2007, 5:19am UTC](https://boards.straightdope.com/t/3-way-cfls-how-do-they-work/423375 "2007-10-20T05:19:34Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [October 20, 2007, 5:19am UTC](https://boards.straightdope.com/t/3-way-cfls-how-do-they-work/423375/1 "2007-10-20T05:19:34Z")
So, when the living room torchiere’s bulb burned out, I dutifully bought a $10 three-way compact fluorescent lamp and screwed it in place. I was kind of expecting two coils, but there is only one. It works about the way you’d expect – at first. The first position on has a fair amount of light, the second much brighter, and the third marginally brighter than the second. We usually leave it on in the first position because even the dimmest setting is fine for general lighting. Then, after about an hour, the lamp will suddenly brighten to not much dimmer than position two, and position three is only a tiny bit brighter than two is. If I click to off for a few seconds, then back to position one, it’s as bright as it was before I shut it off. Then yesterday, it started a new trick. After it brightens, if I go to position three, after a second or so the lamp will dim, to considerably less then the original position one’s brightness. What is going on? How do 3-way CFLs switch between brighter and dimmer and why does it brighten after being on a while? (I’m guessing something heats up) I’m not complaining as such. Even if the lamp is consuming power at the higher rate when it’s at the dimmer setting, it’s consuming less than the incandescent lamp was at its lower setting. I just want the darn thing to be bright when I want it to be, and not so bright when I want it that way. ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [October 20, 2007, 8:52am UTC](https://boards.straightdope.com/t/3-way-cfls-how-do-they-work/423375/2 "2007-10-20T08:52:34Z")
I have a 3-way CFL (which I can’t examine right now), but I thought it had two coils, or maybe just one and a half. I have not experienced the problems you relate, although the dimmest position doesn’t seem all that dim, and it does brighten somewhat after it warms up a bit. FWIW, you don’t HAVE to use a 3-way bulb in a 3-way fixture, but a 1-way will require 2 clicks each time you turn it on or off. Of course, you do lose that handy “multiple levels of lighting” feature with a 1-way. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [October 20, 2007, 9:10am UTC](https://boards.straightdope.com/t/3-way-cfls-how-do-they-work/423375/3 "2007-10-20T09:10:27Z")
I found a patent for this: > [@](#): > > A screw-in fluorescent light unit having two light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a resistor is added to ballast the lamp for low light output. A bilateral switch device is connected across the resistor to facilitate lamp starting at the low light output. You can also have two ballasts in the base, each activating a different set of U-shaped tubes, but that doesn’t appear to be what you’re looking at. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [October 24, 2007, 2:50am UTC](https://boards.straightdope.com/t/3-way-cfls-how-do-they-work/423375/4 "2007-10-24T02:50:39Z")
Update: Last night the thing died entirely, no light in any position. The base would get warm, though. I took it back to the store (Home Depot) and said I’d really expected more than three weeks out of a $10 light bulb. They concurred. The torchiere now has a 30/70/100 incandescent three-way. I tried.