What Causes a Photocell to Go Bad?

You might be wondering what causes a photocell to go bad. Outdoor lighting is very important because not only does it illuminate the surroundings, it also makes the area more secure. Nowadays, photocells are used in outdoor lighting fixtures to save energy, money, and also to help reduce light pollution. However, like any other lighting fixtures, photocells can go bad. Read the rest of the article below to find out the different reasons why a photocell can go bad and how to fix it.

What causes a photocell to go bad? One of the common reasons why a photocell goes bad is because of loose wiring between the photocell and the main circuit. Take note that there should be a solid connection from the wire that connects the photocell and the lighting circuit. Moreover, there should be appropriate electrical power.

Photocells are usually used in outdoor security lighting. Its purpose is to switch the lights on at dusk and turn it off at dawn. A photocell is designed to be sensitive to light and also to convert light into electrical current. How do you know if your photocell is bad? What are the reasons why photocell goes bad? How do you troubleshoot a photocell? Are photocell and solar cell the same? Check out the rest of the article below for the answer to these questions.

What causes a photocell to go bad
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What are Photocell Lights?

Photocells are electronic devices that can be used for indoor or outdoor lighting. It improves the security of your home by automatically turning on the lights when it gets dark or when they detect motion. Because of their automatic on and off feature, you can save energy and money. We have also shared this article that discusses if one photocell can control multiple lights. Check out the article for more information.

How Do You Know If Your Photocell Is Bad?

There are many ways to determine if a photocell is bad. Take note that a functional photocell reads 1020. If the photocells do not have the same reading, this can mean that the wires are shorted. If this is the case, you need to replace the photocell. You can also check out this article that we have written that discusses if a photocell will work in the shade. We have shared tips and ideas that you can refer to.

Reasons Why Photocells Go Bad

Some of the reasons why photocells go bad include extraneous light, dust and shading, electrical, and incorrect settings. Let us learn more about these reasons below.


Electrical issues can cause the photocell to go bad. There are lighting fixtures that are controlled by a separate photocell unit that plugs into the light. There are instances wherein electrical connections can fail which can cause the security light to stay on all the time. This can also be caused by a loose wire or a defective connector. Take note that the electric current should pass through the photocell switch for the light to turn on.

Dust and Shading

Another reason why photocells go bad is because of dust and shading. If the lights remain on during the day, it can be that the photocell is not getting adequate light. This can be because dust has accumulated on the photocell. If the lighting fixture is shaded by some object, it can also cause it to turn on even in the daytime. For the lighting fixture to properly function again, clean the area around the photocell to remove dust making sure that daylight reaches the cell.

Extraneous Light

One of the reasons why photocells go bad is because of extraneous light. For instance, if a security light that uses photocells shut off unexpectedly during the night, this can be because light falls on the photocell and causes the output current to increase. To find out if the lighting fixture has this issue, you can place an electrician’s tape over the photocell. If the light stays on, you can fix the problem by shading the photocell from extraneous light.

Wrong Settings

Another reason why photocells can go bad is because of wiring settings. A lot of outdoor lights have small dials that allow the user to set the light level so that the fixture turns on and off. The light will not operate if the characteristics or settings of the photocell have changed. Check the manual for instructions on how to correct the settings. You can adjust the dials or screws to increase or decrease the sensitivity of the photocell.

✅ Video – Photocells Troubleshooting

Wave Lighting, LLC shared the video below on YouTube. It discusses how to troubleshoot photocells. You can watch the video below for tips and information that you can refer to.

How to Troubleshoot a Photocell

To troubleshoot a photocell, there are a few steps that you need to do depending on the type of problem that you are dealing with. Photocells are current resistors. This means that when strikes the cell, the current flows at decreased resistance. When the light fades, the current diminishes. Moreover, photocells are programmable which means that they can be calibrated for specific applications. Take note that photocells are complex systems so you need to determine the issue in order to provide the proper solution. Below are some steps on how to troubleshoot a photocell.

Step 1 – Disconnect the Photocell

The first step is to disconnect the photocell from the terminals so that you can determine if it is functioning properly. Place the photocell to the controller and directly hook it to the controller terminals.

Step 2 – Tape the Photocell

The next step is to wrap the photocell using black electrician tape. Program the controller to come on in about three to five minutes and to cut off in about five minutes. Next, remove the tape from the photocell and check if the lights come on and off. Repeat the process several times. If the lights operate correctly, then the photocell is working properly.

Step 3 – Repeat the Process

Make sure to repeat them several times to make sure that the light does not come on. Next, check the lights and find out if they repeatedly come on and go off, or remain on despite tape coverage. If this is the case, then maybe it is time to replace the photocell.

Step 4 – Reinstall the Photocell

The next step is to re-install the photocell and connect all of the wires into the controller. Make sure that it properly functions once it is hooked back up. Test it several times. If the photocell is functioning normally, then the photocell and its wiring are not the issues. On the other hand, if the photocell does not function while it is connected to the wires, then the problem can be caused by the wires which should be replaced.

Step 5 – Test the Sensor

The next step that you need to do is to test the motion sensor. Remove the motion sensors and photocell from the controller terminals and directly attach them to the controller terminals. Place the sensor away from your body making sure that there is no nearby obstruction. Next, read and follow the user manual to set the sensor for a one-minute duration time. Next, wave your hand in front of the sensor.

Step 6 – Operate the Sensor 

Wait for the lights to come on. Make sure to repeat the process and see if the sensor performs correctly. If it does, then the lighting is functioning properly. If the same problem occurs, it might be best to replace the sensor. Properly reconnect the wiring of the lighting fixture.

What Happens to a Photocell if it Goes Bad?

If the photocell goes bad, the light will not operate. This is because the electric current that is required for the light to switch on should pass through the photocell switch. We have also shared this article titled, why does my dusk to dawn light stay on all day? Read the article to learn more about the topic.

How to Test a Photocell?

There are many ways to test a photocell. An easy way to do this would be to use a multimeter in resistance-measurement mode. Connect the multimeter to the two leads and find out how the resistance changes when you shade the photocell with your hand.

What Direction Should a Photocell Face?

The best direction to face photocell is on the north and away from direct sunlight. Take note that for a photocell to function efficiently, avoid placing them in shaded areas. On the other hand, photocells can also face west, east, or even downward. Make sure that the photocell is not facing any artificial light sources at night. We have also shared this article titled, why do photocells face north? Check out the article to learn more about the topic.

Is a Photocell and Solar Cell the Same?

A photocell and solar cell are not the same. The difference between the both of them is that a solar cell produces power for electrical circuits, while a photocell is a control switch that is light-activated. Moreover, photocells have been used since the mid-1900s, while solar cells have only been used since 1990. However, both solar cells and photocells need light to work. You can also check out this article that discusses if all photocells are the same. We have shared an in-depth discussion about the topic.


In this article, we have discussed what causes a photocell to go bad. We have found out that there are different causes why a photocell can go bad. Hence, it is very important that you determine what the problem is so that you can fix it properly. Thank you for reading!

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