If your fluorescent bulbs flicker, most likely the problem is with the bulb itself. If the bulb is very dark on either end, it may be defective and burned out. The best way to test the functionality of a bulb is to put it into a fixture you know works. If the bulb doesn’t work or flickers in a working fixture, you know the problem is with the bulb and not the fixture. The problem could be with the starter in your bulb, but most new bulbs do not have starters. However, if your bulb has a starter, you should be able to see it at the bottom of the bulb! Fluorescent bulb starters generally look like gray metallic cylinders and require a simple replacement!
Flickering fluorescent lights can also be a result of temperature. If the air around the bulb is cold and circulating, the bulb won’t be able to generate enough heat to work properly. The internal temperature of a fluorescent bulb should be about 50 degrees Fahrenheit for it to work properly and optimally. If the air around the bulb is too cold, you can use an enclosed light fixture to help insulate the bulb. It’s also possible that you may be using the wrong type of fluorescent bulb that is simply not compatible with your ballast.