How to Replace a Fluorescent Light Ballast? – 9 Steps


Written by

Thomas Carter



Marcos E. Williamson

how to replace a fluorescent light ballast

If you have fluorescent light fixtures at home or in the office that are being stubborn, refusing to turn on, dimming, changing colors, or flickering, then you probably have faulty ballasts and will have to do some lighting ballast replacement.

Luckily, it is not too difficult to replace ballast in light fixtures on your own. You just need to know the steps to take and have the right tools.

In this blog post on how to replace a fluorescent light ballast, we will walk you through everything. So, by the end, you can replace light ballast by yourself without breaking a sweat.

Fluorescent Light Ballast Replacement Guide: Steps to Replace a Ballast


Whether you intend to change a ballast in a 4 bulb fluorescent light or change ballast in fluorescent light with 2 bulbs, you can pick up the instructions here. Read on!

What You Will Need to Have:

  • Screwdriver
  • No-contact voltage tester
  • Utility knife or wire stripper
  • Nut driver or socket wrench

Step 1: Turn Off The Power.


Before starting your ballast light replacement process, switch off the power to your fixture. This will ensure that you will not accidentally electrocute yourself while replacing fluorescent ballast. Do not forget to confirm that the power is definitely down by flipping the switch on – off at least once before starting the process.

Step 2: Remove The Cover Of The Light Fixture.


Next, take the cover of the light fixture off. In most cases, you will just need to pop or twist it off. But some will be screwed on, so you must seek help from a screwdriver.

Step 3: Remove The Bulbs.


After the cover is detached, you can remove the bulbs. Work on one bulb at a time. Simply twist it to expose its metal contacts and pull gently to slide the contacts out.

Be very careful during this step to avoid injuring yourself. Bulbs can break and/or explode! You should set them aside somewhere safe as you continue to replace ballast fluorescent light.

Afterward, take a bit of time to examine the sockets. Repair or replace them if necessary.

Step 4: Remove The Casing/Housing Of The Ballast.


When the bulbs are gone, you will see the casing or housing of the ballast itself. Typically, it is in the center of the fixture.

The next step is to remove ballast cover from fluorescent light fixture. This way, you can access the fluorescent ballast internal components.

As with removing the light fixture’s cover, you may have to seek help from a screwdriver if the casing/housing uses screws. But some will just be snapped into place, so you just need to push the sides together for removal.

Step 5: Disconnect The Wiring.


Once the interior of the ballast is exposed, you will work on the wiring to install ballast. Use a no-contact voltage tester to ensure that the power is not on before touching any wiring.

If the reading states no voltage, grab a pair of cutting pliers to snip all the wires. Next, strip the wires to get about 0.5 inches of them bare with a utility knife or a wire stripper.


Before disconnecting all of the wiring to replace fluorescent light ballast, take a picture of the ballast and its wiring setup. You can refer back to it when you have to install the new ballast.

Step 6: Remove The Old Ballast.


Then, move onto unscrewing the old ballast for ballast removal. All you need to do is loosen the mounting nuts and pop the ballast out.

Generally, there are two mounting nuts. A nut driver or socket wrench will come in handy. When you change light ballast, make sure to support it with one hand to keep it from dropping.

Step 7: Install The New Ballast.


After removing ballast from light fixture, you can go ahead and install a new replacement fluorescent ballast.

This involves two small steps. First, mount it in. Second, connect the old ballast to new ballast wiring with twist-wire connectors. Here, the key is to match the colors of the wires.

It is essential to get a compatible new ballast for fluorescent light ballast replacement. The easiest way to make sure that you get the right ballast for the fix is to bring the old ballast with you to the store.

You can compare your old one with the new options that you have. Check that the fluorescent light ballast wiring, voltage, and current are the same. Also, look at the wattage, length, and type.

Step 8: Reassemble The Parts That Were Detached Earlier.


Now, you will start working backwards. Reattach the casing/housing, put the bulbs back in, and reassemble the cover of the light fixture.

Step 9: Test The Fixture.


Finally, switch the power back on to test your changed fixture. See if it lights up and if you have been successful with changing ballast for your fluorescent bulb.

Frequently Asked Questions


How to tell if fluorescent bulb or ballast is bad?

Look at how your fixture is performing. If it is not turning on, dimming, changing colors, and/or flickering, there is a good chance your bulb or ballast is faulty.

You can also take a closer look at them physically. Bad ballasts can have a deformed housing and burn marks or traces of moisture and oil leaks.

In these cases, you will need a fluorescent lights ballast replacement.

Is replacing ballast T12 with ballast T8 possible?

If you are removing ballast from fluorescent light fixtures and keeping the same setup (aka pulling one out and putting the other in), then no. To use a T8 ballast instead of a T12, you will need to change the lamp before you can change ballast on fluorescent light.

And if you still not define what T8 and T12 ballast looks like, this guide will help you do that.

Can you change fluorescent bulbs to LED?

Yes. LED tubs can go straight into existing fluorescent fixtures if they are the ballast-compatible types. In the case that you have retrofit bypass LED tubes, you will have to do a bit more work and get rid of the ballast.


As you can see, light fixture ballast replacement is a totally doable one-man job. When you need to make the change, just follow all the steps that we have listed for you on how to replace a fluorescent light ballast.

Gather the materials you need in advance, and remember to start by switching off the power and testing that it is definitely down for your safety.

Good luck with your magnetic/electrical ballast replacement!

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