This 1980s light fixture was making this bathroom look very dated. Replacing it is not hard. Before you start the job, be sure to take these safety precautions: Switch off and tape off (or lock out) the breaker to any circuit being worked (turning off the wall switch is not enough as someone could inadvertently switch it back). Use a non-contact voltage detector to verify the breaker/power is off. Check all wires as some wiring conventions allow the hot wire color to vary (three way switches and fans); always use insulated tools and wear insulated gloves if possible.
Remove the existing light bulbs. Be careful as they may be hot and stubborn ones can break off in the socket base. Every light is different, your steps for removal may vary. Usually wall lights are secured with two or more knurled or decorative nuts. There may also be small screws on the sides of the light holding it to the mounting plate. Once the light is separated from the base, check all wires for voltage. If all is safe, remove one wire nut at a time, separate the wires and screw the wire nut back on the wall side. Remove any screws holding the light base to the wall.
Once the old light is completely removed, determine whether there is an existing electrical box. Older homes are likely not to have a junction box. Adding one now is smart for structural reasons as well as electrical safety. In our case, not only did the existing light lack a junction box. but the fixture sat off center from the mirror because of a wall stud. Ceiling boxes are available as shallow as ½” for placement right over a structural unit like our large mirror. If your light is not at a wall stud, an “old work” renovation boxes are available with swing out tabs to mount directly to the drywall. Use a 4” hole saw to remove the drywall and mount the new box. Be careful to move wiring out of the way first and only cut deep enough to get through the drywall.
Install the new light base plate to the box. Be sure to run the circuit wires through a knock out hole. Level the base plate in the vertical or horizontal position depending on your style of light. Now is also a good time to fill any old mounting holes that won't be utilized or covered up.
Start by installing the bare copper grounds from the wall and the light to the green screw on the base mounting plate. Next join the white wires together with a new wire nut, then the black wires. Tuck everything neatly into the junction box.
Mount the new light being careful to tuck any loose wires into the base. You may need to adjust the mounting studs on the base plate out so the decorative nuts can be installed. Loosely tighten and level the light before final tightening.
When the new light is fully connected and installed, make sure the wall switch is off. Flip the breaker that was turned off and make sure it stays on for at least 10 seconds before returning to the light. Test the light with the wall switch.