How to Change the Ballast on a Fluorescent Light Fixture

November 23, 2021 by No Comments

Standard fluorescent light fixtures are much more efficient than incandescent fixtures and last a lot longer. Sometimes, however, the ballast inside the fixture may need to be replaced. The age of the fixture will determine the type of ballast that is used.

What is a Ballast?

Ballasts, also known as control gears, are small devices that are found inside the light. They supply enough voltage to turn on the light and regulate the current flow to it.

Electronic ballasts can be used on newer fixtures and older ones that have been upgraded. They are quieter and more efficient than the older magnetic ballasts. Electronic ballasts are also less susceptible to problems.

Magnetic ballasts are used in older fluorescent fixtures. They can become dangerous. The ballasts that emit a hum when the lights turn on can be magnetic. If they become corroded, they can drop a substance like black tar into the fixture. It’s time for a ballast replacement if your lights flicker or suddenly stop working (and you are certain it isn’t due to bad sockets or bad tubes).

Make sure you find a replacement ballast that has the same wiring configuration as the original. If possible, choose an electronic ballast. Compare the cost of an electronic ballast with the cost of a new fixture. Sometimes it is a better investment than to replace the whole fixture.

Before You Begin

Switch off the appropriate breaker (or box) in your home’s panel to turn off the power to the circuit that contains the light fixture. To disconnect power from a fixture that has a plug and cord, unplug it.


It is not enough to turn off the light switch that controls the fixture. Always turn off a circuit breaker that controls the circuit powering the fixture.

What you’ll need

Equipment / Tools

  • Non-contact voltage tester
  • Optional: Smartphone or digital camera
  • Wirecutter
  • Socket wrench or nut driver
  • Wire strippers


  • Replacement ballast
  • Wire nuts (wire connectors)


Take off the cover

  1. The diffuser cover or lens should be removed from the fixture. Some fixtures come with a clear plastic lens that wraps around the fixture’s outside. Grab the cover at the fixture’s outer edge and pull it down. Look for locking clasps that can pull down the lid to allow the lens to slide down.

Take out the Fluorescent Tubes

  1. Take out the fluorescent tubes (light bulbs). Turn the bulb 90° until you can see the metal contacts. Pull down gently on one end until the contacts fall out of the socket. The bulb should be removed from the fixture. Continue the process with the remaining tubes.
  2. This is the time to inspect the sockets that hold the tubes at the ends of each light fixture. They should be replaced or tightened if they are damaged or loose.

Take off the cover plate.

  1. The wiring cover plate is usually located in the middle of the fixture. There will be tabs on either side of your cover that catch in slots in your fixture. To remove the tabs from the slots, squeeze the sides of your cover inwardly. Then pull the cover down. This will expose the ballast’s wiring.

Disconnect the Ballast Wires

  1. The ballast will have white and black wires. These are the power source cables. Before touching any wires, or connecting wires to them, verify that the power is off. To confirm this, use a non-contact voltage tester to test each wire. This should show that no voltage is present in the wires.
  2. There may be more than one wire connecting the source wires to the fixture’s bulb sockets.


  1. Take a picture of the wiring and ballast with your smartphone or camera so you can refer to it when installing the new ballast.
  2. You can disconnect all ballast wires by taking out the wire connectors. Separate the wires or use a wire cutter to cut the wires near the ballast.

Take out the ballast.

  1. To prevent the ballast from falling, support it with one hand. Then use a socket wrench or nut driver to remove the bolts or mounting nuts. The fixture can be removed from the ballast.
  2. If you don’t already have the ballast, bring it with you to the hardware shop to get a replacement.

Get the wires ready.

  1. You can remove about 1/2 inch of insulation at each end of each fixture wire if you have to cut them earlier or if they are damaged. Wire strippers are useful in this situation.

Mount the New Ballast

  1. Use the bolts or nuts to mount the ballast to the fixture. Use wire connectors to connect the ballast wires with the fixture wires. Install the wiring cover plate, light bulbs, as well as fixture lens.
  2. Turn on the circuit breaker to restore power. Then, test the fixture to ensure proper operation.

Get rid of the old ballast.

  1. Follow the local authorities’ recommendations for proper disposal.

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