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How to Replace a Light Ballast

Fluorescent lights require a ballast to produce light. When this goes out, don’t throw away the light; just replace the ballast. Learn more from Mr. Electric.

Flickering, humming fluorescent lights? Before you toss your whole fluorescent fixture, consider a fluorescent light ballast upgrade. Fluorescent lights need a ballast to produce light. Replacing the ballast will return your fluorescent lights back to full operation, and the task takes just 10 minutes. If you don’t know how to replace a light ballast, worry not, the pros at Mr. Electric have you covered…

How to Replace a Ballast in a Fluorescent Light

  • Gather Tools & Materials
    • Voltage tester (non-contact)
    • Wire cutter/stripper
    • Wire nuts
    • Socket wrench
    • Smartphone/camera
  • Cut Power
    Turn off power to the light at the breaker box, then unplug the light if possible.
  • 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 down.
  • 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 socket and remove the bulb(s). While you’re in there, check the sockets holding the bulbs, tightening/replacing as necessary.
  • 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 the sides of the cover in to release the tabs from the slots, pulling down to remove the cover.
  • Check for Voltage
    Before touching any wires/connections, check for power with a non-contact voltage tester.
  • Take a Pic
    Take a photo of the wires for reference when hooking up the new ballast.
  • Disconnect the Ballast Wires
    Disconnect each ballast wire, removing the connectors or cutting the wires as close to the ballast as possible.
  • Remove the Ballast
    Support the ballast with your hand to keep it from falling while using your socket wrench to remove the nuts/bolts. Remove ballast from the fixture.
  • Find & Purchase the Replacement Ballast
    A replacement ballast can be found either by taking the part number from the ballast or by removing the ballast and taking it 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 on the old ballast). When possible, opt for an electronic ballast, which is more efficient and quieter than older magnetic styles.
  • Prep Wires for the New Ballast
    Removed damaged/crimped portions of ballast wires, stripping ½-inch insulation from ends using wire strippers.
  • Install the New Ballast
    Mount the new ballast to the fixture using mounting nuts/bolts and your socket wrench. Connect the new ballast wires to the fixture with wire nuts, referencing your photo an ensuring a match to the original wiring.
  • Reinstall Light Components
    Put the wiring cover plate back in, followed by the bulbs and the fixture lens.
  • Restore Power
    Flick the circuit breaker back on and plug-in the light, testing for proper operation.
  • Dispose of the Old Ballast Carefully
    Older ballasts (made before 1979) often contain PCBs, a known environmental toxin. If your old ballast is leaking a black, tar-like substance, handle it carefully, avoiding skin contact and taking it to the nearest hazardous waste disposal site.

Now that you’ve upgraded your lights, Is It Time To Replace Your AC or Heater? Our Experts Weigh In.

No matter your electrical quandary, your friendly neighborhood professional at Mr. Electric can help. Contact us and start rapidly running through your to-do list today.

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.