How to Troubleshoot Fluorescent Lighting

The most likely culprits when a fluorescent fixture does not work (or flickers, or fails to start every time) are a worn-out tube or bulb or a faulty socket connection.

Difficulty: Moderately challenging

Instructions

Things You'll Need:

• Neon Tester
• Cloth Or Cotton Swab
• Replacement Tubes Or Bulbs
• Tape And Pen
• Contact Cleaner
• Drill And Drill Bits
• Ladder
• Screwdriver
• Wire Cutters/strippers
• Replacement starter, sockets, ballast and/or fixture

Check a tube and its sockets

1. Remove the diffuser, if any, to access the tube or bulb; twist the tube to remove it (you may need a ladder). Replace a worn-out fluorescent bulb that's blackened at the ends or that has bent or broken pins.

2. Make sure that the socket is not cracked or broken, that it is tightly secured to the fixture housing and that the metal contacts hold the tube securely in the socket.

3. In very humid climates, the pins and contacts can oxidize. Clean them with contact cleaner and a cloth or cotton swab. Don't use sandpaper or other abrasives, which can ruin protective coatings.

4. Old fixtures may have a small cylindrical device, called a starter, that screws into the fixture just below one end of the lamp. To remove and replace it with a matching starter, press in and turn it as you would a childproof cap.

Replace a faulty socket

5. Shut off power to the circuit at the main service panel; remove the tube(s) and the cover plate, which is typically secured at one end by a clip and at the other by a screw.

6. Double-check that the power is off using a neon tester. Probe under the wire connector on the black or red wire connections with one lead, and to the bare ground wire or metal box with the other.

7. Unhook or unscrew the faulty socket from the fixture housing.

8. Use wire cutters/strippers to cut off the wires at the socket and strip off about 1/2 inch (12 mm) of insulation from the ends of the two wires using the 14-gauge hole.

9. Wire the replacement socket by pressing the ends of the wires into push-in terminals or wrapping them clockwise under the screw terminals and tightening the screws.

10. Snap or screw in the socket and test the light. If it still doesn't work, replace the ballast or the entire fixture, depending on the value of the fixture and the cost of a replacement ballast.

Replace a fixture

11. 

    Having tested to confirm the power is off (see "Replace a faulty socket," above), disconnect the house wiring (black, white and bare-copper wires) that feed the fixture.

12. Tape together and label any wires grouped under a single connector; this will make rewiring easier.

13. Remove the mounting screws unless they fit into keyhole openings, in which case simply loosen them.

14. Lower the fixture enough to access the cable clamp that secures that cable to the fixture, then pull out the wires. Or remove the nut that secures the cable clamp to the fixture housing.

15. Compare the mounting-hole locations on the new fixture with those on the one you're replacing. Drill new holes as necessary.

16. Secure the cable clamp to the new fixture and attach the fixture to the ceiling with screws.

17. Rewire with wire connectors. Reinstall the cover, lamps and diffuser, if any.

Tips & Warnings

• Some light gray coloring at the end of a used fluorescent bulb is normal.
• If any wire at a terminal connection sticks out from under a screw head, remove it to cut off excess wire, then reinstall it.
• If your fixture is in an unheated garage and it's cold out, a standard fluorescent fixture may turn on or brighten slowly. Special cold-weather ballasts can fix the problem, but they're costly.
• The heavy pins on single-pin 8-foot (2.4-m) lamps are much more reliable than those on dual-pin models, so if you need an 8-foot (2.4-m) fixture, choose that type.
• Don't remove the cover until you have shut off the power. That could cause a hidden loose wire to short.