How to Wire a T12 Ballast

Ballasts are electrical devices that control the flow of voltage to fluorescent light fixtures. Over time, ballasts can wear out or malfunction and must be replaced. There are different grades of ballasts with differing specifications, of which the T12 is one standard. Installing a new T12 ballast is relatively uncomplicated and can be accomplished with some basic tools and techniques.

The lifespan of a fluorescent light can be extended with the installation of a new ballast.

Step 1

Turn off the power leading to the light fixture's circuit at the circuit breaker panel. Remove the cover to the light, and take out the tubes. Cut the wires leading to the current ballast as close as possible to the ballast, using a set of wire cutters. Loosen and remove the screws holding the old ballast in place, and remove the ballast from the lamp.

Step 2

Remove 1/2 inch of insulation from the ends of each of the wires you cut in the previous step, using a set of wire strippers.

Step 3

Match the colors of the existing lamp wiring to the colored wires of the new ballast. Slip a wire nut over the bare ends of each wire pair, and twist it until it's holding the wires tightly in place. Wrap a short piece of electrical tape around the base of each of the wire nuts and wires leading into them for extra security.


  • Never attempt to work on live electrical circuits.

About the Author

Based in Virginia, Nichole Liandi has been a freelance writer since 2005. Her articles have appeared on various print and online publications. Liandi has traveled extensively in Europe and East Asia and incorporates her experiences into her articles. She holds a Bachelor of Arts in history from West Virginia University.