How do I Diagnose Ballast Issues?

A small box inside the light fixture contains a circuit known as ballast that limits the flow of electrical current to a fluorescent light bulb. The life span of ballast diminishes when a one or more conditions remain unresolved. Attend to faulty ballast as soon as you can to reducing humming or buzzing. Use a process of elimination to diagnose and confirm the existence of malfunctioning ballast.

A buzzing fluorescent light signals ballast trouble.
  1. Turn the light switch off. Use a stepladder and screwdriver to remove the light diffuser from the fixture. A ladder will allow you to reach the lens of the fixture. Use the screwdriver for removing screws that fasten the diffuser to the fixture.

  2. Conduct a temperature check if the lamp refuses to turn on. Most ballasts require a temperature of 50 degrees or higher. When the temperature of the room drops below that number, the ballast may not function.

  3. Listen for a sound coming from the light fixture. Noise can come from a loosely mounted ballast. Check for and eliminate rattles and vibrations. Check the tightness of all the elements within the fixture. When a ballast makes an excessively loud buzzing or humming sound, it may need replacing.

  4. Use a voltage meter to check the voltage in your electrical line if the ballast cycles continuously. Replace the ballast when the meter indicates sufficient power in the line for ballast operation.


  • Exercise caution when handling a ballast. Do not touch any oil leaking from the ballast. The oil contains chemicals that may burn or irritate unprotected skin.
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