Fluorescent Light Ballast Replacement

Fluorescent lights have their quirks. Maybe yours are flickering like a haunted house, buzzing like a beehive, or just refusing to turn on.

Before you toss the fixture or give up on fluorescent lighting, it might be time for a fluorescent light ballast replacement.

The ballast, that unassuming metal box tucked inside the fixture, is often the reason fluorescent lights stop working.

The good news? Replacing a ballast is something many confident DIYers can handle. And if not, we know a few Colorado electricians who can help.

This guide covers everything from how ballasts work to how you can safely replace one step by step.

What Is a Fluorescent Light Ballast (And Why It Matters)

A fluorescent light ballast controls the electrical current going to the bulbs. Think of it as a traffic cop for electricity, keeping the flow steady and safe.

When a ballast goes bad, you might notice:

• Flickering lights
• Humming or buzzing sounds
• Lights that do not turn on
• Darkened or blackened bulb ends

Replacing the ballast can fix all of the above.

How Do You Replace the Ballast in a Fluorescent Light?

We’ll break it down step by step. This applies to most standard fluorescent fixtures, including T12 and T8. If anything looks confusing or unsafe, call a licensed electrician, especially if you’re in Colorado.

Tools & Materials You’ll Need

You only need a few essentials:

• Voltage tester (non-contact)
• Wire cutter/stripper
• Wire nuts
• Screwdriver or socket wrench
• Work gloves
• Step ladder
• Flashlight
• Camera or smartphone (to take a photo of the wiring)
• Replacement ballast (we’ll help you choose)

Optional: a good playlist to keep the vibes up.

Step 1: Turn Off the Power

Head to your breaker box and turn off power to the fixture. Then use a voltage tester to confirm there’s no electricity flowing.

Step 2: Remove the Bulbs and Cover

Take off the lens or diffuser from the light. Then twist the fluorescent tubes 90 degrees and gently pull them out. Set them somewhere safe.

Step 3: Take Off the Wiring Cover Plate

Look inside the fixture for a metal plate covering the wires. Squeeze the tabs or unscrew it to remove the cover. You’ll now see the wires and the ballast.

Step 4: Confirm the Power Is Off

Use your voltage tester one more time. Double-checking keeps you safe.

Step 5: Take a Picture of the Wiring

Snap a quick photo of the wiring setup. This gives you a reference when it’s time to hook up the new ballast.

Step 6: Disconnect the Ballast Wires

Cut or disconnect the wires close to the ballast. You’ll usually find the ballast connected using wire nuts or quick-connect terminals.

Step 7: Remove the Old Ballast

Use a screwdriver or socket wrench to loosen the screws holding the ballast in place. Once free, remove it from the fixture.

Step 8: Get the Right Replacement Ballast

Bring the old ballast or its part number to a hardware or lighting store. Match the following:

• Lamp type (T5, T8, or T12)
• Voltage (usually 120V or 277V)
• Number of lamps
• Start method (instant, rapid, or programmed)

Pro tip: Choose an electronic ballast for quieter, more energy-efficient lighting.

Step 9: Connect the New Ballast

Strip ½ inch of insulation from each wire if needed. Use your photo as a guide to connect the wires with wire nuts. Typical colors:

• Black and white: power
• Blue, red, or yellow: lamp wires

Tuck wires back inside the fixture.

Step 10: Mount the New Ballast and Cover

Screw the new ballast into place. Then snap or screw the wiring cover plate back on.

Step 11: Reinstall the Bulbs and Fixture Cover

Put the tubes back in and rotate them to lock in place. Reattach the cover.

Step 12: Restore Power and Test

Turn the breaker back on. If all is well, your lights should turn on instantly, no flickering, no buzzing.

Bonus Step: Properly Dispose of the Old Ballast

Older magnetic ballasts may contain PCBs (toxic chemicals banned by the EPA). If your ballast is leaking or labeled as pre-1979, take it to a hazardous waste facility. Do not throw it in your regular trash.

When to Call an Electrician

Not comfortable handling wiring? That’s okay. Call a pro if:

• The fixture is in a commercial space
• You’re unsure about the wiring
• The ballast connects to multiple lights
• You just want it done fast and right

Book a licensed electrician in the Denver metro area today. We’re experts in lighting, panels, and emergency repairs.

Final Thoughts: Fix Your Lights Without Losing It

Replacing a fluorescent light ballast is a manageable DIY project for many homeowners. Just follow the steps, stay safe, and know your limits.

And if you’d rather skip the tools and ladders? The Electricians have your back.

Call us, message us, or schedule service online, we’ll bring the light back to your home or business.

Got lighting questions? We’re here to help.