How To Repair Fluorescent Light Fixtures

Here is how to troubleshoot a fluorescent light fixture that will not turn on or flickers. Many times when a fluorescent light starts to flicker or takes a long time to turn on the ballast or light starter is going bad. If just one of the fluorescent tubes does not light (with a fixture with 2 or 4 bulbs), obviously it could be a burned out bulb. Before doing anything that involves replacing parts, try the DIY steps below to fix it yourself.

To troubleshoot a fluorescent light fixture: First start by making sure you have power being supplied to the light fixture. If flipping on the switch does not turn the light on, check the circuit breaker. Once you confirm you have power going to the light, the next thing to do is make sure the fluorescent tubes are not burned out. If you have only one bulb out, it is most likely just that bulb has burned out and replacing it should fix the problem. If all of the tubes DO NOT turn on, then most likely it is a bad ballast. However it is possible for all bulbs to burn out at once but this is not likely. To rule out a bad tube or bulb, you need to determine if you actually have a burned out tube.

To determine if the bulb or bulbs are burned out, install new fluorescent bulbs into the fixture. To be completely sure, replace all bulbs to be certain it is not a bulb issue. If the tubes light up then you know you have a bad bulb or tube. If the light still continues to not light up or it just flickers, then a starter or ballast is most likely bad. Most newer fluorescent light fixtures do not have a starter. The newer fixtures just have a ballast. So if you turn on the light and no bulbs light up even after the bulbs have been replaced, change out the ballast. Most common T8 ballast for 2 bulb light – Most common T8 ballast for 4 bulb light – New fluorescent light fixture 2 bulb – New fluorescent light fixture 4 bulb

If you would like to test the ballast to be sure it is bad before replacing it, follow these steps:

First turn off power. (turn off power at the breaker)
Remove bulbs.
Remove the metal cover that shields the ballast.
Turn power back on.
Turn on your voltage detector and hold it next to the wires supplying power to the ballast.
If power is being supplied to the ballast but not out to the bulbs, it is a bad ballast and needs to be replaced.

To remove and replace the ballast, follow these steps: There are many different types of fluorescent lights. Your light fixture may be slightly different from the description we provide but the principal is the same.

First turn off power. We recommend to turn the power off at the breaker to prevent accidental power being supplied to the light while you are working on it.
Remove the bulbs.
Remove the metal cover that shields the ballast.
Find out the type of ballast your light fixture has. Purchase the same type of ballast or compatible at your local home improvement store or online. NOTE: Sometimes a ballast is MORE EXPENSIVE than a completely new fluorescent light fixture. Do some research to find out which is cheaper before you purchase anything.
Once you have your new ballast, remove the old ballast by following the instructions that came with the new ballast. (If no instructions were provided, you can usually just cut one of the old wires from the old ballast and wire it to the new ballast according to colors and markings on the wires. Doing this one wire at a time can help you wire the ballast correctly and with less confusion if no instructions are provided)
Once the old ballast is removed, screw the new ballast into place using the screws provided. Wire it up according to the schematic and instructions provided. If you have to cut wires, it is recommended to use electrical tape on top of the wire nuts for reasons of safety.
Once the new ballast is wired up, replace the ballast cover.
Install the fluorescent tubes back into the fixture.
Turn the light back on and test to be sure the light works.