How to Fix a Fluorescent Light

Inside a fluorescent light, electricity is delivered to a ballast, which sends a spark through the mercury-vapor-filled tube (or bulb), creating light by activating phosphors that coat the inside of the tube. If any of the components are faulty, the light won’t work right. Once you pinpoint the problem, most fixes are very easy. Remember to turn off the power first!

fix fluorescent light©Don Vandervort, HomeTips

A fluorescent light doesn’t work right when the bulb begins to fail. When the light alongside this medicine cabinet stopped working, replacing the bulb was all that was needed.

An old tube blinks off and on just before it dies; repairs are often simply a matter of replacing it. This problem may also occur because of poor contact between the pins at the ends of a tube and the tube holders. If the pins are bent, use needle-nose pliers to straighten them. Clean the pins and socket contacts with fine sandpaper.

Though gray bands at the ends of tubes are normal, black bands indicate that the tube needs to be replaced. If only one end is dark, turn the bulb end-for-end. If the tube is new and these fixes don’t work, you may have to replace the starter or ballast.

Some fixtures (“A-rated”) are quieter than others, but most fluorescent lights have a slight hum. If the sound seems too loud–or if you can smell electrical burning–shut off the power. The ballast is probably either the wrong type, improperly installed, or defective. Replace it or call an electrician.

Brand new tubes tend to flicker, as do bulbs that are cold. If an old tube still flickers after it has had a chance to warm up (or after you’ve warmed up the room), rotate it a couple of times in the tube holders. Try cleaning the tube”s end pins. If it still doesn’t work, replace it.

If only the ends of the tube glow, either the starter or the ballast is defective. Replace the starter, then the ballast.

Replacing a Fluorescent Ballast

You can replace a ballast or tube holder if you’re fairly familiar with wiring.

1Turn off the power to the circuit.

 

2Remove the tube and the cover plate that conceals the workings.

 

3Disconnect or cut the wires to the tube holder or ballast and remove.

 

4Strip 1/2 inch of insulation from the ends of the wires.

 

5Mount the component and connect the wires with wire nuts.

6Re-place the cover and tube.

 

7Turn the circuit back on.

 

8Turn the switch on.

Replacing a Fluorescent Light Starter

Although newer fluorescent fixtures have built-in starters or no starters at all, most older lights have an easy-to-change, visible starter. It is a small, silvery cylinder that plugs into one of the tube holders.

1Shut off the switch.

 

2Remove the tube.

 

3Give the starter a quarter turn in a clockwise direction, and pull it out.

 

4Plug in a new starter, giving it a quarter turn counterclockwise.

 

5Re-place the tube.

 

6Turn the switch on.

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Join the Conversation

  • Steve Albaya

    Takes for ever to light just flickers so replaced the tube -no improvement this is a 3ft tube with no starter evident Help please

  • jacksonbrown

    All four lights out after wireless alarm guy checked my system. He said there might have been a power surge, nothing he did would have caused all four lights to quit. Ballast was warm when removed a few days later. Replaced ballast and still no lights, have not replaced bulbs yet. Ballast was a little less that 10 years old, two of the bulbs were replaced a couple years ago. House is 10 years old.

  • john

    i have replaced tube and starter no problem works fine until i switch of then on

  • Gary Gressel

    8 ft fluorescent light fixture. replaced the bulbs. circuit is running through the bulbs but no light… Help

    • Don Vandervort, HomeTips

      Try turning the bulbs a bit to see if they go on with better connections at their ends. If that doesn’t work, you probably need to replace the ballast.

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