How to test a fluorescent ballast

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When a fluorescent light fixture is buzzing, flickering or not turning on, the ballast may be malfunctioning. A qualified electrician can safely troubleshoot problems in your fixture. If you would like to do the troubleshooting yourself, however, opening the fixture to examine and test the ballast can help you determine whether it's causing the problem.

Turn off the power running to the fluorescent light fixture.

Open the lens and remove the lamps and ballast cover. If you notice any obvious signs of wear on the ballast, such as cracks or leaks, the ballast needs to be replaced.

Check for loose or exposed wires. Make sure all wires are making proper connections that follow the diagram shown on your ballast.

Set the multimeter to the continuity function. Touch one prong to a power wire on the ballast and the other prong to the neutral wire. In a ballast, blue or yellow wires are the power and the white is the neutral. If the multimeter fails to light up or beep, a problem with the ballast is keeping the circuit in the fixture open and the ballast needs to be replaced.

Replace the ballast cover and lamps before turning on the power.

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