Replacing a Fluorescent Tube Fixture Ballast

Whenever you are going to troubleshoot fluorescent tube fixture ballast you must know that the fixtures consist of at least lamp(s), lamp holders, ballast and internal wiring, and if you own and older version of fixture, it might have ‘starters. Ballast is one of the important parts of a fixture because it is used to create the voltage and current which is necessary to start and illuminate your fluorescent lamp. If the need arises for you to replace faulty ballast, there are two types of replacements that you may consider. The first one is the modern electronic variety that runs cooler which does not hum and also lights up your tubes faster. The other one is the old-fashioned magnetic ballast which is prone to humming and also takes a few seconds to lights up.

What you need to do:

  1. Stepladder
  2. Wire stripper
  3. Voltage tester
  4. Insulating tape
  5. Side cutters
  6. Correct size nut driver
  7. Replacement ballast
  8. Twist-on ceramic wire connectors
  9. Replacement fluorescent tube

Fluorescent Tube Fixture Ballast


  1. First of all, for safety precautions, you must ensure that your breaker switch that controls the lighting circuits are turned off. Meanwhile, you must turn off the light switch to the fluorescent fitting that you are working on.
  2. It is recommended that you work together with a helper especially when you are using a stepladder and the person would also be available to hand parts down to your helper.
  3. The covering lens of the light fixture lens needs to be removed. Next step is for you to turn the fluorescent tube until you are able to see the two prongs on each end of it are lined up with the slots in the fixture. Always do this gently because the tube is fragile.
  4. The long metal cover that spans the surface behind the fluorescent tube sockets need to be squeezed on one side of it and this cover is a compression-type cover that can fit into two grooves. Once it has been popped it out, you will notice an oblong black box that has wires connected onto it, which is known as the ballast.
  5. You would be able to see a prong on your voltage tester and try pressing the prong against the terminal where the black feed wire that connects to the ballast before you start to press the button on your voltage tester. Make sure there is no reaction on the tester which means the line is dead and it is safe for you to proceed with your work. If your tester lights is on, that means you have isolated a wrong breaker when turning off your electricity or it might be there are two lighting circuits attached to the fixture. Try to turn off your main power switch again and retest the black wire one more time making sure that there is no electricity is flowing through it.
  6. There are black and white wire connectors that lead to your ballast, which need to be unplugged. Then, you need to wrap around the connectors using a piece of insulating tape before bending the wires out of the way.
  7. Next, you need to snip through the colored wires that sprouts on each end of your faulty ballast by using a pair of side cutters and then, you must cut at least 3 inches of the wires from the ballast.
  8. After that, the ballast needs to be removed by unscrewing the mounting nuts by using the correct nut driver. If you are not sure the type of ballast, bring the ballast to your electrical supply store so that you can make comparison and look for the correct type for your ballast replacement. You also need to look for a dozen of twist-on ceramic wire connectors and a replacement fluorescent tube.
  9. Once you have the new ballast, you can proceed by installing the new ballast. Make sure that you snip through the colored wires at least 3 1/2 inches from the ballast using your side-cutters. Then, strip off at least 1/2 inch of insulation from the ends of all the colored wires leading to and from the ballast using a wire stripper.
  10. Ensure that you follow the colors and connect the ballast wires. You need to hold the wires parallel to each other before twisting the bare ends securely together. For example, the blue wire to the blue, red to red and yellow to yellow. Once finished, you must ensure that you tighten the connection by screwing a ceramic wire connector securely onto the ends of your twisted pair of colored wires.
  11. Next, the black and white wires need to be reconnected back and also insulate the connectors by wrapping a piece of insulation tape around them.
  12. After that, proceed with the fluorescent tube replacement, reconnect back the power at its breaker from the main switch and test its operation whether it is working fine or not.

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Additional Reading:

New Fix-It-Yourself Manual: How to Repair, Clean, and Maintain Anything and Everything In and Around Your Home