# Why is my CFL flickering?

**URL:** <https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792>\
**Category:** Factual Questions\
**Created:** [July 7, 2007, 12:55am UTC](https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792 "2007-07-07T00:55:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [July 7, 2007, 12:55am UTC](https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792/1 "2007-07-07T00:55:34Z")

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I put a compact fluorescent light bulb in one of my outdoor sockets, which is controlled by a timer. The timer is a replacement for a wall switch. When the timer is off, the bulb flickers, instead of going completely out. How can it be flickering if it is supposedly getting no current? Or is the current just low enough to be under the threshold to light an incandescent bulb but not a CFL?

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [July 7, 2007, 1:06am UTC](https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792/2 "2007-07-07T01:06:58Z")

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Probably your timer is switching the current on and off via an SCR or triac; these can sometimes be leaky enough to provide a voltage source at high impedance to your load which is your CFL, in this case. The current would be very low; enough so the CFL’s ballast may try to ignite the bulb, but not enough to get it to start. I suspect that’s what’s happening here.

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**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\
**Post date:** [July 7, 2007, 1:08am UTC](https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792/3 "2007-07-07T01:08:43Z")

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Update: I discovered that the other two (standard) bulbs on the same switch were both burned out. I just replaced them, and now the CFL doesn’t flicker anymore. That seems even weirder to me.

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [July 7, 2007, 1:13am UTC](https://boards.straightdope.com/t/why-is-my-cfl-flickering/410792/4 "2007-07-07T01:13:49Z")

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[QUOTE=CookingWithGas]  
That seems even weirder to me.  
[/QUOTE]

Makes perfect sense, actually. With the new bulbs providing a low-impedance path for the leakage, there isn’t enough left to make the CFL flicker.