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How to repair fluorescent lights and ballast

Caution: Before removing a fluorescent tube or working on the fixture, turn off power to its circuit.

If a fluorescent lamp fails to light, check the service panel; replace a blown fuse or reset a tripped circuit breaker, if any. If the tube still doesn’t light or if it flickers or blinks, turn off power to the fixture and twist the tube slightly back and forth to make sure it’s firmly seated in the sockets.

If that doesn’t work, give the tube a quarter turn toward you and pull it out. Handle the tube carefully. Use long-nose pliers to straighten a bent tube pin. Spray the socket contacts and the pins with electric contact cleaner. Clean a dirty tube with a damp cloth; let it dry before reinstalling it. Tighten the socket screws; replace broken sockets.

To reinstall the tube, line up the pins with the socket slots, push the tube in, and give it a quarter turn. Still no light? Install a new tube of the same wattage and type. A new tube may flicker for an hour or two at first. If flickering lasts longer or if the new tube doesn’t light, replace the starter with a new one of the same wattage. Rapid- and instant-start fluorescents don’t have starters.

Blackening at the ends of a tube means that it’s worn out; replace it. If only one end of the tube is discolored, remove it, turn it over, and reinstall it.

If the ends of a tube glow, but the center does not, replace the starter.

If the lamp still doesn’t work, hums loudly, or repeatedly blows a fuse on a circuit that isn’t overloaded, the ballast, which regulates the flow of power to the tube, may be defective. Turn off the power and remove the tube and the screws holding the lid to the channel (the ballast maybe attached to the lid or to the channel). First check the ballast for loose or incorrect wiring; tighten the mounting screws and all electrical connections. Compare the wiring with the diagram on the ballast; reattach the wires if necessary. If the problem persists, remove the ballast. Note how its wires are connected and disconnect them; unscrew the mounting screws. Replace the ballast with a new one of the same type and wattage or with a low-noise type.

Troubleshoot a circular fixture as you would a lamp with straight tubes. To remove a circular tube, turn off power to its circuit, grasp the tube in both hands at the collar, and carefully pull down until the pins come out of the socket; disengage the tube from the tube clips. To install a new tube, gently turn  the collar to align the pins with the socket. Hold the tube in both hands and, with thumbs, press the pins into the socket. Push the tube clips in slightly with your middle fingers, and slip the tube into place.

Frequent turning on and off wastes power and shortens tube life. When leaving a room for a short time, leave the lamp on. Most fluorescents won’t work below 50° F. Warm the room or install a low-temperature ballast.