Symptoms
- Steady hum or buzz coming from the fixture
- Hum present even when the tube looks fine and lit normally
- Hum has gotten louder over time
Likely causes
- CommonNormal magnetic ballast humOlder magnetic ballasts naturally produce a faint 60Hz hum that's not necessarily a problem.
- CommonA failing ballastIncreasing hum, especially paired with flicker or a burning smell, points to ballast failure.
- PossibleA loose ballast mountingA ballast that's come loose from its mount can vibrate and hum more than normal.
- PossibleAn electronic ballast with a failing componentEven quieter electronic ballasts can develop an audible hum as they fail.
What to do
- Note whether the hum is faint and constant or getting louder over time.
- Check if the hum is paired with any flickering, dimming, or a faint burning smell.
- Turn off the fixture if you smell burning and don't turn it back on.
- Turn off the breaker and check that the ballast is mounted securely, if you're comfortable opening the fixture.
- Replace the ballast if humming is new, increasing, or paired with other symptoms.
- Consider converting to an LED tube retrofit, which eliminates the ballast and its hum entirely.
- Have an electrician handle ballast replacement or LED conversion if you're not comfortable with the wiring.
Tools and parts
Replacement ballastSearch: “fluorescent fixture ballast”
LED tube retrofit kitSearch: “LED tube ballast bypass retrofit kit”
When to call a pro
Call an electrician to replace a failing ballast or convert the fixture to an LED retrofit.
Safety
Use caution
Turn off the fixture and its breaker if you smell burning, and don't ignore a hum that's getting noticeably louder.