How to Replace a Light Ballast
- 1). Unplug the fluorescent fixture or shut off the power to the socket at the fuse box.
- 2). Remove the ballast cover using a socket wrench to remove the nut attachment or by unclipping the cover. That exposes the wiring underneath.
- 3). Cut the old ballast wiring several inches away from the ballast using sharp wire cutters.
- 4). Unscrew the ballast using a socket wrench to remove the mounting nut. Hold the ballast while your unscrewing it to keep it from dropping.
- 5). Place the new ballast in place of the old unit. Have someone hold the light in place.
- 6). Twist the wires of the new ballast to the old wires leading to the light. Cover the connected wire with a wire nut to protect the connection. Restore power and test the light.
Source...