How to Troubleshoot Fluorescent Light Fixtures. A fluorescent light fixture that is not working or working well can be caused by several problems. Diagnosing which problem you have and how best to tackle it is a fairly simple job that you can do on your own.
Verify that the fixture has power by making sure the switch is on and the breaker to the area is not tripped.
Look at the bulbs to see if any of the lamps are broken.
Replace any lamps that are broken or not lighting. Turn on power to see if the fixture works with the new lamps.
Inspect the sockets where the lights plug in for cracks or other visual breaks. Sometimes these break due to heat and could be causing your problem. If you find a broken socket, replace the fixture.
Use a circuit tester to check for power at the fixture itself.
Change the ballast in the fixture if it's less expensive than simply replacing the fixture. This requires some electrical knowledge, but is a fairly simple job.