How to Replace a Fluorescent Light Ballast

A dingy old white fluorescent light fixture with two fluorescent light tubes emitting orange light.

Are you tired of flickering, humming fluorescent lights? Before you toss your whole fixture, consider a fluorescent light ballast replacement. Fluorescent lights need a ballast to produce light. The ballast regulates the amount of electricity flowing to the bulb. Replacing this component will return your fluorescent lights back to optimal operation, and the task can take as little as 10 minutes.

If you don't know how to replace a light ballast, don't worry! The pros at Mr. Electric® have you covered.

How to Replace a Ballast in a Fluorescent Light

Time Required: About 10 minutes

Materials Needed: Voltage tester (non-contact), wire cutter/stripper, wire nuts, socket wrench, gloves and smartphone/camera

  1. Gather tools and materials.
  2. Cut power.
    If possible, unplug the fluorescent light fixture. Or, turn off power to the light at the circuit breaker. You should never perform electrical work on items that are still active.
  3. Take the cover off the fixture.
    On fixtures with a clear plastic lens surrounding the fixture, remove the cover. If your fixture has a framed lid, look for the clasps. These pull down and allow you to swing the lens open.
  4. Remove the fluorescent light tubes.
    Twist the bulbs about 90-degrees. When you see the metal contact located at the ends of the bulb, gently tug down until the contacts slide out of the sockets. While you're in there, check the sockets holding the bulbs, tightening or replacing as necessary.
  5. Take off the cover plate.
    The wiring cover plate in the center of the fixture must be removed to expose the wires. Visually locate the tabs that hold the cover in place, then squeeze in the sides of the cover to release the tabs from the slots, and pull down to remove the cover.
  6. Check for voltage.
    Before touching any wires/connections, verify that there is no power flowing to the fixture with a non-contact voltage tester.
  7. Take a picture.
    Take a photo of the wires, which you can then reference when hooking up the new ballast.
  8. Disconnect the ballast wires.
    Disconnect each ballast wire by removing the connectors or cutting the wires as close to the ballast as possible.
  9. Remove the ballast.
    Support the ballast with your hand to keep it from falling and use your socket wrench to remove the mounting hardware. Remove the ballast from the fixture.
  10. Find and purchase the replacement ballast.
    A replacement ballast can be found either by taking the part number from the ballast or the ballast itself to a lighting supply store for a replacement. Make sure the new ballast matches the wiring diagram, voltage, and current of the old one (these details can usually be found stamped or printed on the old ballast). When possible, opt for an electronic ballast, which is more efficient and quieter than older magnetic styles.
  11. Prepare wires for the new ballast.
    Remove damaged or crimped portions of ballast wires by stripping ½-inch insulation from the ends using wire strippers.
  12. Install the new ballast.
    Mount the new ballast to the fixture using mounting hardware and your socket wrench. Connect the new ballast wires to the fixture with wire nuts. Reference your photo as needed to ensure a match to the original wiring.
  13. Reinstall light components.
    Put the wiring cover plate back in, followed by the bulbs and the fixture lens.
  14. Restore power.
    Flick the circuit breaker back on and plug in the light to test for proper operation.
  15. Dispose of the old ballast carefully.
    Ballasts made before 1979 often contain polychlorinated biphenyls (PCBs), a known environmental toxin. If your old ballast is leaking a black, tar-like substance, handle it with caution and avoid skin contact. Always take old ballasts to the nearest hazardous waste recycling site for proper disposal.

a fluorescent light ballast

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No matter your electrical quandary, your local Mr. Electric can help. From simple lighting upgrades to whole-house rewiring, Mr. Electric is the one to call. You can schedule an appointment online or call us at 844-866-1367 for all your electrical needs.

This blog is made available by Mr. Electric for educational purposes only to give the reader general information and a general understanding on the specific subject above. The blog should not be used as a substitute for a licensed electrical professional in your state or region. Check with city and state laws before performing any household project.