Unlike incandescent and LED lights, fluorescent lighting requires a ballast that sends the correct amount of power into the bulb or tube.
The ballast delivers enough voltage to start the lighting process. Once the illumination begins, it regulates the current to ensure a steady light output.
Without a ballast, fluorescent bulbs would use the 120V current and quickly burn out, damaging the lamp. If the ballast malfunctions, you’ll notice visible or audible signs, which means it's time for a potential replacement.
A failing ballast often causes buzzing sounds or flickering bulbs. Since these issues can also occur in normal operation, verify the ballast condition before replacement.
Here are the steps to follow to check if the ballast is bad in fluorescent light.
1. Turn Off the Power
Turn off the fixture at the circuit breaker before checking the ballast. For extra safety, confirm that no voltage is present. If the switch no longer activates the light, it is safe to proceed.
Next, remove the lens cover. Depending on the design, it may wrap around the fixture or be secured with slides or screws. Be careful to avoid breaking it.
2. Remove the BulbsOnce the cover is gone, remove the fluorescent bulbs from your light fixture. If they are circular, you'll see a plug that connects the product to the ballast. Straight and U-shaped bulbs are installed in sockets that connect them.
To remove U-shaped bulbs, gently pull them against the tension spring until they release from the socket.
For linear tubes, twist the bulb a quarter-turn in either direction until it loosens and slides out.
3. Remove the Ballast Cover
Once the bulbs are out of the fixture, remove the ballast cover if this component isn't already exposed. Most covers attach with slot inserts or screws. If it's leaking oil, swollen, or showing burn marks, remove it. If you're unsure, proceed to the next step.
4. Check the Ballast with a Multimeter
Turn the multimeter to its ohm setting. If you have multiple options available, set it to the X1K resistance range.
Insert one probe into the wire connector while holding the white wires together. Touch the other probe to the ends of the yellow, red, and blue wires coming from the ballast. Some might exclude the yellow.
If the ballast doesn't cause the needle to deflect, replace it. A good one will cause the needle to move or display a resistance reading.
5. Install the New Ballast
Replace the old ballast with a new one. Install the cover again, replace the fluorescent bulbs, and then restore power to test the fixture.
If it works as intended, the lights will turn on without buzzing or flickering. It may take a couple of minutes for the fixture to stabilize before the symptoms disappear.
If the fixture does not work, go back to check the bulb connections, the ballast, and other connections. Continue to recheck until you receive power to the lights. Once the fluorescent lights turn on, replace the fixture cover.
When replacing a faulty ballast with a new one, you'll need to have access to the fixture. Since most are installed on ceilings, you'll want a stepladder that can reach that space.
Although it might be tempting to stand on a chair or another piece of furniture, the ladder is the safest way to work on the unit. Have someone spot you to prevent falls while you're checking the lights and ballast.
If you have a ballast that keeps shorting or burning out, there could be a deeper wiring issue to fix. This problem could also be evidence of a short in the line.
Once you've replaced the ballast and still have persistent flickering or humming, it is time to call in an experienced electrician to look at the issue. When dealing with electricity, it's always better to take extra precautions.
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