A fluorescent electronic ballast is a device that helps fluorescent lighting fixtures glow. While compact fluorescent lights do not have ballasts, traditional light fixtures that use the long bulbs do. Troubleshooting the ballast of a fluorescent light is a fairly basic test. In order to do so, you will need to have a few tools and a basic understanding of how the high voltage transformer works.
Step 1 - Disconnect the Electrical Power From the Light
Before beginning, you will need to shut off the electricity running to the light. ELECTRICITY IS NOT TO BE CONSIDERED LIGHTLY, IT HAS SERIOUS HAZARDS AND CAN BE DANGEROUS IF PROPER PRECAUTIONS ARE NOT TAKEN. THE BREAKER FOR THAT CIRCUIT MUST BE SHUT OFF AT THE MAIN PANEL, after which you will need to wait a few moments to allow any stored current within the ballast to dissipate in the lighting circuit. Remove the fluorescent bulb from the fixtures that hold it in place at either end; these parts are also known as tombstones. Fluorescent bulbs are extremely fragile, so set them somewhere where they will not get broken.
Step 2 - Remove the Protective Covering and Observe the Ballast
Using a screwdriver, remove the protective covering that hides the ballast, and take a look at it. If you notice that there is oil leaking from it, you will need to replace the entire thing. Leaking oil indicates that the internal seal has been ruptured by excessive heat.
Step 3 - Testing the Ballast
To determine the problem, you’ll need to first test the ballast. Using your Multimeter, test the high voltage side for continuity between the wires that go to the tombstones. Typically, there is either one or two wires that go to each fixture. Blue or yellow wires indicate power wires and white will be the neutral wire.
Turn the multimeter to the “ohms” setting and test its batteries by placing the ends of the two probes together. The meter should indicate a direct short. If not, the batteries need replacement or its internal fuse is gone. Next, you need to touch one of the probes to the white wire and the other probe to one of the colored wires coming from the ballast.
If your meter doesn't get any reading, the ballast will need replacement. If you get all readings around the same value when measuring between the white and any of the colored wires, the ballast should be functional, showing a continuous circuit. Once all the wire pairs check as functional, move on to testing the low voltage side of the ballast.
Step 4 - Testing the Low Voltage Side of the Transformer
If your ballasts all tested well, you will need to test the low voltage side of the transformer. Start by removing the nuts from the black and white wire that come from the power feed side of the ballast. Touch the probes of your volt-ohm meter to the black and white wires. If your ballast is properly functioning, it will show a continuous circuit. If not, then you will need a replacement.
If you have tested your ballasts on both the high and low voltage sides and it appears to be functioning correctly, check the wire connections from the tombstones. Sometimes one wire can come loose and cause your ballast to not function properly.