by Benjamin Allen
When a fluorescent light doesn’t work properly, the problem could be with the bulbs, the lamp holders that support the bulbs, or the ballast or starter — or it could be that electricity isn’t getting to the light.
You can’t dispose of bulbs or ballast in your regular trash. If you replace them or the entire fixture, contact your waste disposal company to find out how to dispose of them properly.
Bulbs
If the fluorescent light fixture is in a particularly dirty area and the bulbs are exposed, wipe the bulbs clean.
If the bulbs aren’t dark grey or black at the ends, turn on the light and gently wiggle the bulbs to seat them properly in the lamp holders at each end.
If the ends of the fluorescent bulbs are dark grey or black at each end, they’ve burned out. Replace them with new bulbs of the same length and wattage. Don’t throw away the old ones — they contain mercury. Contact your local waste service to learn where to dispose of the bulbs safely.
Lamp Holders
The lamp holders that hold each end of a fluorescent bulb can crack or bend if you bump them when installing a bulb, preventing contact with the bulb ends and disrupting the flow of electricity. Turn off power to the light at the supply panel or fuse box and then inspect the lamp holders. Replace them if they’re damaged.
The Ballast or Starter
The ballast. The ballast of a fluorescent light fixture supplies the voltage that makes the gas inside the bulb glow. It’s a rectangular black metal box that’s about 8 inches long inside the fixture.
One sign of a failed ballast is a loud hum. Another sign is black goo leaking from the ballast, which you can detect by turning off power to the light at the supply panel, opening the fixture and inspecting the ballast.
Replacing a failed ballast can cost more than replacing the whole fixture. If you decide to replace the ballast, follow the wiring diagram provided with the new ballast.
The starter. A few fluorescent lights use a starter instead of a ballast. If the light takes a moment to go on after you flip the switch, and the bulbs flicker for a moment, it's likely the light fixture uses a starter. If the light flickers longer than usual or flickers all the time, the starter is failing.
To replace the starter, twist it counterclockwise a quarter turn and remove it. Take it to the store with you and buy an exact replacement.
Power
It’s possible that the problem isn’t with the light, but with the power supply. The switch or the wiring could be the problem. Before checking either, turn off power to the light at the supply panel.
The light switch is the most likely part of an electrical circuit to fail. For instructions for checking and replacing a light switch, see Test and Replace a Light Switch.
If the switch isn’t the problem, yet no power is reaching the light fixture, it will take significant sleuthing to find where the circuit is broken. A call to an electrician might be warranted.
Ben Allen was the editorial director for more than 100 home improvement books and is almost constantly working on his 1912 home.
