Troubleshooting dusk-til-dawn flood lights

Dusk-til-dawn flood lights may have any of a variety of configurations and features that could be involved in a failure. The simplest involve a fixture with photo sensor that interrupts (switches) power to the floodlight lamp holders when daylight is present. Other ‘enhancements’ such as outdoor motion sensing (aka ‘electronic eye’) flood lights and dual brightness level settings may come at the cost of increased susceptibility to weather, mechanical and electronic failures (usually due to temperature extremes or else voltage surges from nearby lightning strikes, damaging circuitry inside the sensor assembly). Where possible, consider use of an astronomically-self-calibrating timer, rather than sensor-based controls for outdoor lights. If photo-sensing, and especially motion-sensing, are critical or cheaper due to the wiring configuration of your fixture(s), then consider a whole-house surge suppressor to protect their sensitive electronic components along with those of consumer electronics and newer appliances inside the home.

A timer may be the culprit if your outdoor lights don’t seem to operate correctly in Spring or Fall: daylight savings time, your own pattern of being outdoors vs. indoors, and changing daylight hours could individually or cumulatively amount to the timer being out of sync with your lighting needs. The most common timer for exterior lighting is a 9″ x 5″ mechanical clock with set-screw timing points that trip a mechanical switch on and off. The Intermatic T101R has been a go-to classic for decades, but may be effectively replaced today by the astronomically auto-adjusting digital version for location in utility areas, or a more elegant wall switch timer that you can locate for convenient manual override to turn your floodlights on/off when the timer would otherwise prevail.

Photo sensors may take anywhere from 10-120 seconds to respond to continuous illumination (turning off), and a similar duration of darkness before turning on. This tends to minimize flickering and contactor fatigue from responding prematurely to marginal conditions, such as at dusk and/or with passing cloud cover when light levels are already low (such as when the sensor is in a shaded location).

Dust to dawn flood lights won’t come on

Dusk to dawn flood lights won’t turn off

The most common cause of a flood light fixture not coming on (or not turning off) is that the small electronically-controlled contactor in the sensor has frozen in the open (off) or closed (on) position. Tapping on the device during the condition (light or dark) when the contactor is ‘out of position’ (malfunctioning) may free it for normal operation for several more years — ie: indefinitely. Once you’ve tried this and verified that lamps are good and any associated light switches/timer switches and circuit breakers are on, replacing the sensor is the next step. For some fixtures with integrated light and motion sensing, this may mean replacing the whole fixture. For others, the sensor may be located mounted to the same enclosure where the outdoor flood fixture is attached — or remotely, probably at another fixture location outdoors. Contact us for assistance with non-functioning flood lights, anytime.

My flood lights turns on and off all night long.

How to stop a flood lights from turning on and off all night?

General use CFL lamp not intended for flood lights

A standard CFL-type lamp may shine enough light into the photo sensor to activate its ‘daylight’ sensing mode.

Outdoor-rated directional flood lights, CFL-type

A directional lamp casts little light on the photo sensor mounted behind it.

Photo sensors are light sensors — not just sunlight. A flood light that turns on and off at intervals of 10-120 seconds may be a multi-sensor type flood fixture whose motion sensor is responding to a habitual animal visitor, or it may be that the photo-sensor is responding cyclically to the light of the fixture(s) it controls. When daylight is gone, the photo-sensor turns on the lamp. The sensor receives light from the lamp for about 30 seconds before turning itself off. After about 30 seconds, the sensor decides it really is dark out, and turns back on. Repeat until dawn.

One should take care to install outdoor-rated, directional flood lamps, or to locate the fixture and aim the lamps in such a way that there is no direct ‘line-of-sight’ between the lighted part of the lamp (bulb) and the sensor.

Contact us for assistance with blinking flood lights, or any other outdoor lighting issue, anytime.

See also:

  • Automatic self-calibrating dusk to dawn lighting timer switch
  • Floodlights and fixtures at
    • Heath/Zenith is major manufacturer of many electronics, and a budget maker of outdoor fixtures, sensors and sensor-fixtures. Home Depot and others stock this brand, as well as competitor Lithonia, which is a store brand of one of the big box home improvement stores.
    • RAB is a higher-end outdoor fixture and sensor manufacturer, whose products are more likely to survive minor voltage surges resulting from nearby lightning strikes or major events such as short circuits or large motor start-stop cycling on the building electrical system.

      RAB is a higher-end outdoor fixture and sensor manufacturer, whose products are more likely to survive minor voltage surges resulting from nearby lightning strikes or major events such as short circuits or large motor start-stop cycling on the building electrical system.















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  • hi….ive bought i outside floodlight….a ed206 230w pir halogen floodlight……when it gets dark the light comes on for 20 secs, then off, then on,then off…..etc……what is the problem please

    • Sounds like the lamps are somehow shining on the photo sensor. Try aiming as directly AWAY from the sensor as possible (even if that isn’t where you want to aim them). This is a troubleshooting step that may confirm that light leakage onto the sensor (or an over-sensitive sensor) is the problem. Next step is to try different lamps (230W may be too bright — or WAY over the lamp rating of your fixture, or both), or a different fixture.

  • thankyou robert……i chaanged the light for another light and this one is ok now…..the other one must have been faulty….thankyou for the reply

  • Nothing works even the power led that tells you that the board is getting power don’t light but the power at the board is there.
    Open for suggestions.

    • Power at the load but no load function = bad load. I don’t do the electronics part. I’d say it’s time to return the item and replace with new. Home Depot or Lowe’s will accept most anything for exchange or store credit, with or without receipt. Items from better suppliers or hardware stores will carry a decent warranty and the supplier (some hardware stores?) will take the item back for replacement with new good one. As I know all too well, installation is much of the cost — usually most of it. So this is only somewhat good news.

  • Hi,

    I have an issue, the gas fumes from the boiler keep setting off the security light at the rear of the house & the Neighbours are kicking off?  Can I change something?  

    I had two lights front & back fitted recently and the problem one at the back in the PIR a red light pops on & off when detecting me or gas fumes.  The front light doesn’t have the red light in the PIR, should the lights be swapped from the back to the front & vis-versa?



  • Hi,
    I have an issue, the gas fumes from the boiler keep setting off the security light at the rear of the house & the Neighbours are kicking off?  Can I change something?  

    I had two lights front & back fitted recently and the problem one at the back in the PIR a red light pops on & off when detecting me or gas fumes.  The front light doesn’t have the red light in the PIR, should the lights be swapped from the back to the front & vis-versa?



  • CB writes:

    “Put up a dust-to-dawn light on a pole about two years ago and now the light goes off and on at night. Stays off all day like it is suppose too do. What do I do?”

    Author answers:

    My article discusses the likely cause: the lamp you have installed may cast light in every direction, rather than a projected cone from a proper outdoor flood lamp. The scattered light (often from an indoor type CFL lamp) falls on the light sensor that keeps the thing off during daylight, confusing it into thinking it’s daytime and turning off. After the 30-120 second delay built into the fixture, the absence of light at nighttime causes the fixture to turn on again. After 30-120 seconds of delay, the scattered light again tricks the fixture into thinking it’s daytime, so it turns off. The cycle repeats until actual daylight comes around and keeps the fixture off all day.Fixes include selecting a direction outdoor-rated lamp, and aiming all lamps away from the sensor unit in the fixture or attached to the same box with the fixture.

  • Scott writes:

    Hi Robert,
    I just installed a Dusk to Dawn LED floodlight.
    Now when I turn it on the light flashes 3 times then turns off.

    Any suggestions?

    • This sounds like it could be a test mode or manual override mode. See if there is a selector switch under the sensor, that lets you put the fixture into normal (dusk-to-dawn and/or motion-sensing) mode. Some sensor-integrated fixtures include a feature allowing some off-then-on operation of a standard switch in the circuit, to engage a manual override of the fixture sensing mode. You can make the fixture turn off in the dark when it normally would be on. Or on in the daylight when it might otherwise be off. The 3 blinks may be its indication that such a mode has been engaged.

  • Scott, 

    I believe that some photo and/or motion sensor units, and even some remote timer switches, cannot operate electronically-ballasted high-efficiency lamps such as compact fluorescents (CFL’s) and light emittent diode / solid state lighting types (LED/SSL). These controls rely on the filament of an incandescent lamp to complete the circuit (even when the control is in its ‘off’ mode) and provide a low-current, low-power power source for the control/sensor electronics. The high-efficiency lamps, in contrast, do not ‘turn on’ and allow current to flow through the circuit until full voltage has been applied from the switch/control.

    I’ve not explored this at length, but I do know that some older controls do work with some CFL lamps, and I would imagine that the capacitative integrated power supply used in both CFL’s and many LED’s would appear electrically similar to the controls, so LED’s should also work with some controls. Note, though, that as I’ve said elsewhere, just because ‘it works’ doesn’t mean it’s right. A control that runs operating current through a CFL can cause the CFL to try to start itself constantly, without ever fluorescing. The starter mode of the CFL will then wear out much faster than it would, otherwise.

    A good discussion thread and some recommendations for Westek controllers, may be found at:

  • HILL31 asks:

    I have had a dusk til dawn outdoor wall solar lamp for 8 years.  I noticed the light is not on when it is dark, and is on when it is daylight.  I did not notice this problem before I recently I replaced the bulb with the exact same name, volt, wattage, etc.    

    Any suggestions?  

    • I don’t have a lot of experience with these new self-contained solar fixtures, other than that none I’ve seen deliver bright light. If you have one that accepts standard lamps, it may be relatively robust to what I’ve encountered.

      If you can locate the daylight sensor that keeps the lamp turned off in daytime, make sure it is clean and can see daylight where it is pointed (and don’t point it where the lamps can shine on it during night time). Try giving it a sharp tap with the rubberized handle of a screwdriver or other hand tool (hard plastic handle is probably ok, too). This may dislodge a tiny contactor inside, permitting it to move ‘open’, turning off the lamp in daylight. Then, the small integrated battery may charge enough during daylight to operate for a few hours or more at night.

  • Hi Robert,

    I have 4 dusk to dawn mercury vapor lights (1 on each corner of my commercial building).  There is a receptacle in the top of each for a 3 prong dusk to dawn or I guess you would say photocell sensor.  All my lights are staying on 24 hours a day and will not go off during the day.  I have replaced the dusk to dawn ight controls in 3 of the 4 and they are still not turning off during the day.  What can the problem be?  Thanks

  • A customer writes:

    “I have an outdoor light that is supposed to come on when it gets dark outside but it only seems to come on during daylight hours and won’t come on at all when we need it most.
    Any ideas?”

    • Sounds like a clock got way out of whack. Maybe during an extended power failure? Intermatic is the classic electro-mechanical timer switch. It will typically locate near the main breaker panel and may control one or a whole host of lights. The heavy-duty switch mechanism can open and close circuits serving powerful loads (lots of lighting, or even motors), and the electronics and mechanism are tough enough to withstand power surges — BUT: power outages will cause the clock to fall behind and the super-simple mechanical clock can’t reset itself for creeping changes in daylight hours. This has to be done manually at least twice per year — assuming power outages don’t create even more frequent need.

    • The problem could be something else, but unless there’s a timer switch somewhere, I don’t see how a floodlight would be turning on in daytime but not at night.

      For a good newer digital self-correcting programmable timer, check out:

      Automate timer switch lighting controls

  • Hi

    I have a dusk to dawn LED PIR outdoor light which comes on when I power up but nothing after it goes of. I have powered down a few times with the same result. It initially stays on for about 40 seconds and then nothing.
    Is the sensor failing?

    • Make sure you are testing in darkness — or using the ‘test’ mode.

      If you are powering on during the day, the fixture may have reset itself while off and the photo sensor included along with most motion sensors for flood lights will take 30 – 120 seconds to turn the fixture off due to ambient light. Unless the sensor has a functioning ‘test’ mode, the light won’t come on unless you block out light from entering the photo sensor (a squiggly of copper behind a clear window, usually on the bottom of the sensor head) for 15-120 seconds. Or, until it gets dark enough outside.

  • My outdoor motion light is too bright.

    • Exterior lights may be dimmed with a conventional dimmer (located indoors, since I’m not aware of weather-rated dimmer switches), but such dimming will likely cause problems for most motion and/or light sensors. One option, probably only for new installations or those where new conductors can be pulled through conduit (raceway), would be to place the sensor on the line side of the dimmer, and then bring switched voltage back through the dimmer, and then back out to the exterior lamp holder / lighting fixture. Again, though, you’d want to check manufacturer statements carefully to be sure that the sensor is not sensitive to the operating mode of its load (if it is CFL/LED compatible, then it is probably also able to drive a dimmed lamp — whether it be filament type or high-efficiency CFL/LED).

  • On Jan 21, 2014, at 7:01 PM, — wrote:

    I have a set of four outdoor dusk to dawn flood lights installed, well when the lights come on, only 2 of them are coming on. I thought that maybe the bulbs wear blown, so I changed them out and still they are not on, but like I mention before, one side of them are working and the other side is not.

    • 4 on one fixture? Or two and two on different fixtures?

      If all 4 lamps share one sensor, then it’s likely bad lamps or a wiring error or loose connection.

      If two and two, then maybe one of two sensors is bad. Or if u are looking near dusk, maybe one is more sensitive than the other to remaining light, or located where there is light for longer.

      If u have 4 lamps on one fixture, there’s a good chance one of them is aimed so the light strikes the sensor and it thinks it is daylight.

  • Hello. Do you have any experience with Dusk til Dawn Photocell Sensors? For some reason, mine appears to stop working during Christmas time. It appears to coincide with me plugging in Christmas lights in the wall socket on the side of my house. For example, this year, I plugged in my Christmas lights and a day later my Photocell sensor appeared to stop working. This is two years straight this has happened to me (last year the sensor MAGICALLY started working again).

    NOTE: The sensor looks like the one at this link:

    Do you have any advice on this? Any way that you know of to turn this sensor back to the “ON” position. Any help on this would be greatly appreciated!

    • Sounds as if the position of the Christmas lights is such that they shine on the sensor and give the effect of daylight there.

      Try routing your Christmas lights away from your dusk-to-dawn photo sensor, or find some way to shield the sensor from the Christmas lights.

  • Someone searched:

    “can a light timer control a light of 2000w”

    • Most residential and even commercial/industrial lighting circuits will be 20A maximum, either 120V (residential) or maybe 277V (commercial/industrial). At 120V, allowing for required 20% safety margin, that means .8 x 20A = 16A times 120V = 1920 Watts. Even if the switch/timer could support 2000 W, the circuit cannot.

      A typical residential toggle switch might be rated for 600 W or 1000 Watts. Dimmers typically 600 W or less. An intermatic time-clock timer enclosure with mechanical switching mechanism may be rated for 30A or more, 120V or 240V, so it could conceivably switch .8 (safety factor) * 30A * 240V = 5,750 VA or 5750 Watts. Most switches will give their load rating in Watts. If not, it should have a nominal operating voltage and you can multiply that by the Ampere rating that should also be given for the product. Volts of the actual circuit times Amps capacity of the switch = Watts of lighting you can switch.

  • […] Dusk-til-dawn flood lights troubleshooting Licensed … – Dusk-til-dawn flood lights may have any of a variety of configurations and features that could be involved in a failure. The simplest involve a fixture with photo …… […]

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