# Why would a porch light start strobing and is it cause for alarm?

**URL:** <https://boards.straightdope.com/t/why-would-a-porch-light-start-strobing-and-is-it-cause-for-alarm/813387>\
**Category:** Miscellaneous and Personal Stuff I Must Share\
**Created:** [May 1, 2018, 3:32am UTC](https://boards.straightdope.com/t/why-would-a-porch-light-start-strobing-and-is-it-cause-for-alarm/813387 "2018-05-01T03:32:16Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![aurora\_maire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aurora_maire/32/328_2.png) [@aurora\_maire](https://boards.straightdope.com/u/aurora_maire)\
**Post date:** [May 2, 2018, 4:18am UTC](https://boards.straightdope.com/t/why-would-a-porch-light-start-strobing-and-is-it-cause-for-alarm/813387/21 "2018-05-02T04:18:37Z")

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> [@beowulff](#):
>
> Actually, it’s pretty likely that’s what is happening.  
> If the light is bright, and not aimed correctly, it may be turning itself off due to it’s own light reflected into the sensor. Maybe something in the environment has changed, like a spider web or a leaf or something is now reflecting enough light to make the sensor think it’s “day.” If the dusk/dawn controller doesn’t have enough hysteresis, then it doesn’t take much stay light to flip it’s state.

I’ll check that out tomorrow. I didn’t look at the light when I was over there today. That would be funny if I could fix it. And he would never know I involved a bunch of people on the internet to solve his problem. 🙂

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**Author:** ![aurora\_maire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aurora_maire/32/328_2.png) [@aurora\_maire](https://boards.straightdope.com/u/aurora_maire)\
**Post date:** [May 2, 2018, 11:29pm UTC](https://boards.straightdope.com/t/why-would-a-porch-light-start-strobing-and-is-it-cause-for-alarm/813387/22 "2018-05-02T23:29:20Z")

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I talked to his next door neighbor today and he said the old man is staying at his vacation home right now. The light fixture is a lantern type so we just took the top off and removed the light bulb. I’m not sure what kind of bulb it is but not a regular one. The glass is kind of dirty, so maybe it was reflecting the light back to the sensor. Anyway, problem solved for now. My neighbor said he would talk to the old man when he gets back. Thanks for everyone’s advice!

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**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\
**Post date:** [May 2, 2018, 11:50pm UTC](https://boards.straightdope.com/t/why-would-a-porch-light-start-strobing-and-is-it-cause-for-alarm/813387/23 "2018-05-02T23:50:11Z")

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Oh, good. I am glad you found out what’s going on.

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