What to Know About Changing a Fluorescent Light Ballast

  • 01 of 09

    Fluorescent Ballast Basics

    Fluorescent lights
    Chris Nowitzki / EyeEm / Getty Images

    Fluorescent lighting fixtures contain a transformer device called a ballast. Ballasts on newer fixtures are electronic and are more energy-efficient and quieter than older-style magnetic ballasts. Magnetic ballasts tend to hum when the lights are on and, when they go bad, they can drip a tar-like black gunk down onto the fixture lens. If your lights flicker or turn themselves off -- and you're sure it's not due to bad light bulbs -- it's time to replace the ballast.  

    Be sure to find...MORE a replacement ballast with the same wiring configuration and voltage rating as the original. Choose an electronic ballast, if available. Also compare the cost of the ballast vs. a new fixture; sometimes it's a better investment to replace the entire fixture.

    Supplies Needed:

    • Non-contact voltage tester 
    • Smart phone or digital camera
    • Wire-cutting pliers
    • Nut driver or socket wrench
    • Replacement ballast
    • Wire strippers
    • Wire connectors (wire nuts)
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  • 02 of 09

    How to Change a Fluorescent Ballast: Step 1

    Power Off
    Power Off. Timothy Thiele

    Turn off the power to the circuit containing the light fixture by switching off the appropriate breaker in your home's service panel (breaker box). If the fixture has a cord and plug, simply unplug it to disconnect from power. 

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  • 03 of 09

    How to Change a Fluorescent Ballast: Step 2

    A phot of a fluorescent light lens cover being removed.
    Removing a Lens Cover. Timothy Thiele

    Remove the lens, or diffuser cover, from the fixture. Some fixtures have a clear plastic lens that wraps around the outside of the fixture. Grab the outer edge and gently pull the cover away from the fixture and down. If the fixture has a lens inside of a framed lid, look for locking clasps that pull down and allow the lens to swing down. 

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  • 04 of 09

    How to Change a Fluorescent Ballast: Step 3

    Remove Bulb
    Remove Bulb. Timothy Thiele

    Remove the light bulbs (fluorescent tubes). Grab a bulb and twist it about 90° until you see the metal contacts at its ends. Gently pull down on one end so the contacts slide out of the socket and remove the bulb from the fixture. Repeat the process for the remaining bulbs.

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  • 05 of 09

    How to Change a Fluorescent Ballast: Step 4

    Ballast Cover Removal
    Ballast Cover Removal. Timothy Thiele

    Locate the wiring cover plate, usually in the center of the fixture. On either side of the cover there will be tabs that catch in slots in the fixture. Squeeze the sides of the cover inward to slip the tabs out of the slots, and pull the cover down. This will expose the ballast and its wiring. 

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  • 06 of 09

    How to Change a Fluorescent Ballast: Step 5

    Ballast Wire Connections
    Ballast Wire Connections. Timothy Thiele

    Look for the black wire and white wire connected to the ballast. These are the power source wires. Before touching any wires or wire connections, confirm that the power is off by testing each wire with a non-contact voltage tester. The test should indicate that there is no voltage present in the wires. 

    In addition to the source wires, there may be four or more wires connecting the ballast to the fixture's bulb sockets.

    Tip: Take a photo of the ballast and wiring for reference when installing...MORE the new ballast. 

    Disconnect all of the ballast wires by removing the wire connectors and separating the wires or, if necessary, cutting the wires close to the ballast, using wire-cutting pliers. 

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  • 07 of 09

    How to Change a Fluorescent Ballast: Step 6

    Remove Ballast
    Remove Ballast. Timothy Thiele

    Support the ballast with one hand (to prevent it from falling), and remove its mounting nut(s) or bolt(s) with a nut driver or socket wrench. Remove the ballast from the fixture. Bring the ballast with you to the store to find a suitable replacement. 

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  • 08 of 09

    How to Change a Fluorescent Ballast: Step 7

    Preparing The Wires
    Preparing The Wires. Timothy Thiele

    Strip about 1/2 inch of insulation from the end of each of the fixture wires, using wire strippers, if you had to cut the wires earlier or if the wire ends are damaged. 

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  • 09 of 09

    How to Change a Fluorescent Ballast: Step 8

    Mount the new ballast to the fixture, using the mounting nut(s) or bolt(s). Connect the ballast wires to the fixture wires, using wire connectors, to match the original wiring. Reinstall the wiring cover plate, the light bulbs and the fixture lens. Restore power by switching on the circuit breaker, and test the fixture for proper operation.