How to Change T12 to T8 Lamps

Turn the power off at the main breaker. It is essential that you be sure the power is off. The easiest way is to turn the light fixture on, then have an assistant watch it while you turn it off at the breaker box. When the light goes out, you can be certain you have turned off the proper breaker.

Remove the cover over the fixture, if it has one. This is typically a plastic panel that lifts or snaps in and out of position. Take the old T12 bulbs out of the fixture.

Take the cover off the old ballast. There are many methods for securing covers, so you will need to look closely at yours to see how it is attached. Most likely you will need either a screwdriver or a small wrench.

Cut all wires coming from the ballast. Make your cuts several inches from the ballast itself. Unscrew the bolt or bolts holding the old ballast into the fixture. Depending on how it is attached, you may either need a screwdriver or a socket wrench. Remove the old ballast.

Set the new ballast in place of the old one, and screw it into the fixture with the bolts you removed previously. Strip the insulation back about 1/2 inch from the end of each wire.

Connect the wires from the new ballast to the cut wires in the fixture, being sure to match all of the colors. Secure the wires together by screwing wire nuts onto each connection.

Repeat this procedure for the second ballast in the fixture and then replace the ballast cover. Put the new T8 bulbs into place, and put the cover on the fixture. Turn the power back on to complete the job.