How to Install a T12 Ballast

Turn off the breaker supplying power to the light fixture. Ensure the light switch is set in the “off” position to provide a second means of safety against electrical shock.

Set up a stepladder directly below the fluorescent light fixture. Remove the cover from the light, by either pushing it up and pulling it down or grasping the sides of the cover and pulling one side down firmly. Set the cover aside. Remove all bulbs from the light by turning them a quarter turn and sliding them down. Grasp the inner cap – covering the wires and ballast – with both hands. Pull down on one side of the cover to release it from the holding clamps keeping it attached to the fixture. Set the cover aside.

Remove the wire nuts from both the black and white wires connecting the ballast to the household electric, by turning them both counterclockwise. Untwist the black and white ballast wires to separate them from the house power. Cut all remaining wires 2 to 3 inches away from the ballast with a wire cutter/stripper. Cut 1/2 inch of insulation from the end of each cut wire attached to the fluorescent fixture with the stripper jaws of the cutter/stripper.

Turn the ballast holding screw counterclockwise with a Phillips-head screwdriver. Pull the ballast forward after the screw has been removed. Set the ballast aside.

Slide the tabs of a new T12 ballast into the slot on the fixture housing. Align the front tab with the hole left when you removed the Phillips screw. Set the end of the Phillips screw with the hole. Tighten the screw, by turning it clockwise with the Phillips screwdriver.

Remove 1/2 inch of insulation from the end of each wire coming from the new ballast. Connect the black ballast wire to the black house power wire, by setting the exposed section of both wires together, sliding a wire nut over them and turning the wire nut clockwise. Repeat the procedure with the white ballast wire.

Match the colored wires coming from the back of the ballast with the remaining wires connected to the fluorescent fixture. Ensure all wire connections are tight.

Align the fixture cover with the holding clamps. Push the cover toward the fixture to lock it in position. Install all light bulbs. Install the light cover on the fixture. Turn on the breaker to supply power to the light switch. Turn on the light switch.