Grow lights are an excellent way to start plants indoors before the regular outdoor season begins. They are also useful for those without access to a traditional outdoor garden. For those individuals, a grow light allows for an indoor garden year round. The most popular grow lights are fluorescent bulbs as they are both economical as well as efficient. From time to time, a ballast will burn out on the grow light and will need to be replaced. Luckily, this is a job almost any do-it-yourselfer can handle.
Unplug the grow light from the power source. If the light is wired directly into the home then locate the circuit breaker or fuse box and cut the power from there. Take out the fluorescent tubes or bulbs by turning each tube about a quarter-turn to slide them out of the connection slot, or simply unscrewing the bulb-style tubes.
Remove the protective casing to get to the ballast. At each end of the fixture, find a small clip. On some fixtures you will need to turn it 180 degrees to release it; on other models you may need to press the tab first, and then lift off the casing cover.
Cut the wires connecting the ballast to the fixture a few inches from the ballast. A pair of wire cutters or a strong pair of scissors will work fine. Remove the screws at the ends of the ballast and pull the ballast out of the grow light fixture.
Insert the new ballast and replace the screws holding it in place. Strip 1 inch of insulation from both the ballast's and the fixture's wires with a pair of wire strippers.
Connect the wires from the fixture to the wires from the ballast. Match the blue to blue, red to red, black to black and white to white. Twist the pairs together and secure with a wire nut or electrical tape.
Reattach the fixture's casing, and replace the fluorescent bulb(s). Reconnect the fixture to a power source and turn it on to test.