Why Do My Motion Sensor Lights Keep Flashing On & Off?

Motion sensors, whether on security cameras and lights or on other devices, are supposed to be accurate, right?

After all, it is their job to also detect everything around them with maximum precision in order for the whole system to function properly!

However, what do we do when the motion sensor light isn’t working properly? Doesn’t this make the entire device unreliable? Well, yes, it does. Still, a problem with the motion detector lights is usually just that – a problem with the motion detectors or the lights, not with the entire device.

So, how about we answer the question, “Why do my motion sensor lights keep flashing on and off?”

Whether we’re talking about indoor or an outdoor motion sensor lights, false flashing can be due to multiple different reasons.

A problem with the lights themselves

Very often the motion sensors themselves are perfectly fine but the LED lights are having a problem. In these cases, the motion sensor lights are not so much “turning on and off” as they are just flickering. Flickering motion sensor lights can be caused by several things:

  • A bad bulb or diode. A pretty straight-forward problem, even high-quality lights tend to go out eventually and sometimes even new ones can malfunction.
  • A bad connection between the bulb or diode and the light fixture itself. Maybe they simply aren’t connecting right, maybe there is something obscuring the connection, or maybe the connecting mechanisms are faulty for some reason. Either way, a problem with the connection between the light and the fixture can easily cause flickering.
  • A bad electrical light circuit. Finally, a faulty circuit can also cause a motion sensor light to flicker even though the motions sensors themselves haven’t been triggered.

All three of these problems have nothing to do with the motion sensors themselves but they still need to be resolved. You can’t have your motion sensor light flickering as it won’t be able to do its job. The first thing to do is try and change the light bulb. If that doesn’t fix the problem call an electrician to check the circuit and determine the exact nature of the problem.

A problem with the settings of the motion sensor

Most motion sensors work on the same principle – they trigger when the sense a significant change in the level of heat in their vision (which typically would indicate that an intruder has moved into their field of view). However, there are many reasons why this would happen – maybe the sensor isn’t positioned properly or maybe its settings aren’t set adequately. Either way, what you basically need to do is try and reset the motion sensor and its settings:

  • Try to switch the motion sensors from its default operational setting to its “test” setting. Most motion sensors, especially in security cameras have a test mode. This setting is meant precisely for the purposes of such scenarios – to check how and if the motion sensor works and to reset it.
  • Make sure to reposition the sensor adequately so that it’s facing the way it is supposed to be facing. If when you open up the device you notice that the sensor is facing the wrong way this can immediately indicate the reason for the problem – it’s possible that there was something, a tree or anything similar, that the sensor was detecting. So, just reposition the motion sensor in such a way that it’s both capturing the field you want it to and it’s also not getting any interference from trees, activity on the streets or sidewalks, etc.
  • Adjust the motion sensor’s range if necessary. It’s quite common that the range of motion sensors is set to maximum even though it is not supposed to be. If that has happened then it is likely that the motion sensor was detecting some actual movement but it was movement outside of your property and doesn’t really concern you, causing “false positive” turning off the light. Lower the range to as much as you need it to be and the sensor should be alright from then on.
  • Activate the “pet immunity” mode of your motion sensors if you have pets. In fact, even if you don’t have pets but your neighbors do, or you know that there are a lot of stray animals around your property, consider activating pet immunity on your motion sensor lights. This mode which can be found on most modern motion sensors works by preventing the sensor from triggering when animals below a certain weight range pass through them. As long as you adjust that weight range accurately then it will stop triggering every time a cat passes by but it will still work when a human gets inside uninvited.
  • Consider the angle range of your motion sensor as well. Aside from the distance range on your sensor, there might also be problems with its motion range. Every motion sensor has an angle at which it operates, usually between 180 and 360 degrees. It’s not uncommon, however, for motion sensors to have wider angles than they are supposed to and therefore capture unexpected movements that they shouldn’t care for. To make sure that this isn’t a factor you can just put two thin pieces of electrical tape on both sides of the motion sensor to narrow its view to what you want it to be. This way you will make sure that the motion sensor is no longer detecting anything from beyond its range.
  • Put the motion sensor back into its active mode. If everything has been done properly and there are no further problems, your motion sensor should work flawlessly from now on.


Blogger, editor, developer who loves green living. Interested in photovoltaics and solar lighting. Reviewing solar products since 2013.

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12 Responses

  1. Test not working. Now what?

    • Arthur says:

      Can you, please, explain a bit more about what you mean by ‘’not working’’?

    • Will Hector says:

      My defiant 180 late just blinks on and off all day-and-night it’s hooked straight to a wall plugin through the wall to outside should always have power worked fine forever about a year 1/2 then just blinks on and off

      • Arthur says:

        You should give reset a try! Turn off the circuit breaker for about 30 seconds to a minute, which often will be enough. If the lights are still not working properly, switch the lights on and off four times (on each position), leaving them off for a few seconds afterward. This is also a method that works on some models. Good luck!

  2. Pam w says:

    Hi Arthur,
    My sensor light worked just fine until someone turned the switch off. I’ve tried flipping the switch a few times but it hasn’t reset. The light comes on for about a minute, shuts off and flashes back on and stays on. Do you know what that is about> Thanks.


    • Arthur says:

      Have you tried resetting the lights? Try turning off the circuit breaker for about one minute. In many cases, it will help. If it fails, you can try switching your light switch on and off for times (on each position), then keep it off for a few seconds. That should also reset the lights.

  3. Terri says:

    My outside motion light started clicking and flashing on & off constantly how do I fix? Help

  4. Tony Ellis says:

    I have 8 SANSI LED Security Lights and all are set to “dusk to dawn” setting. The power to them is controlled by a light switch inside the house (no clue why). When the switch is turned on, they stay off until sundown. Then they come on and immediately start flashing on and off. This is all 8 of them and all are brand new out of the box, installed by an electrician. ideas?

    • Arthur says:

      The easiest fix could be the bulb simply being too loose, in which case you need to screw it tighter. You also need to make sure your photocell isn’t too bright for the photocell, in which case it might turn it off. Sometimes it’s due to using the wrong type of bulb, so make sure your sensors are compatible with the bulbs you’re using. It can also be due to placing, or perhaps you need to create a barrier.

  5. Madhu sudan Dabral says:

    What is the reason for the light to turn off even though the PIR motion sensor moves in front of the light circuit

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