Symptoms
- Tube flickers, especially when first turned on
- Ends of the tube look darkened or blackened
- Flickering gets worse over time or in cold temperatures
Likely causes
- CommonThe tube is nearing the end of its lifeDarkened ends and increasing flicker are classic signs a fluorescent tube needs replacing.
- CommonThe tube isn't fully seated or rotated into its socketsA tube that's slightly loose won't make a full, stable connection.
- PossibleA failing ballastThe ballast regulates power to the tube, and a failing one causes flicker even with a good tube.
- PossibleCold ambient temperatureStandard fluorescent tubes can flicker or start slowly in cold garages or unheated spaces.
What to do
- Turn off the fixture and rotate the tube to make sure it's fully seated in both end sockets.
- Check the ends of the tube for dark or black discoloration, which suggests it's due for replacement.
- Replace the tube with a new one of the correct type and length.
- If a new tube still flickers, or flickers in multiple fixtures with the same ballast type, suspect the ballast.
- Note the ambient temperature, since cold spaces need cold-weather-rated ballasts or tubes.
- Have an electrician replace a failing ballast, since it involves higher voltage during startup.
- Consider converting the fixture to LED tubes or an LED retrofit kit if the ballast is failing anyway.
Tools and parts
- Step ladder
Replacement fluorescent tubeSearch: “T8 fluorescent tube replacement”
Replacement ballastSearch: “fluorescent fixture ballast replacement”
When to call a pro
Call an electrician to replace a failing ballast, since it involves higher-voltage components inside the fixture.
Safety
Use caution
Turn off the fixture's breaker before replacing a ballast, and handle old fluorescent tubes carefully since they contain a small amount of mercury; don't break them and dispose of them per local rules.