If you have an old light fixture that you no longer want in your house and you have purchased a new light fixture to replace the old one, here are a few solutions to common obstacles that you may encounter while swapping out one light fixture for another.
#1 Test The Voltage
Don't assume that the power to your light fixture is out just because you turned off the circuit to the room of the house that the light is located in. Many junction boxes, which is what your overhead light is attached to, often have multiple wires from different circuits in them.
So, before you start working on the light, take a non-contact voltage detector and hold the tip near the wires. This will allow you to make sure that there is no voltage in the wires before you start to work. You don't want to work on a live wire.
#2 Have Extra Hardware On Hand
Don't rely on the hardware that comes with your new light fixture. The default hardware included with your new light fixture many not work with the junction box that you have in your home.
It is a good idea to pick up a few different styles of mounting brackets at your local hardware store before you start this job. They generally only cost a couple of dollars each, and having some extras on hand will allow you to proceed with the job if the mounting hardware doesn't work. If the mounting hardware that comes with the light does work, you can easily return the extra mounting hardware that you purchased.
#3 Use A Wire Stripper To Cut Down Long Mounting Screws
Oftentimes, the mounting screws that will come with your new lightening fixture will be too long for your junction box. If the mounting screws are too long, you don't need to find new mounting screws; instead, you can modify the mounting screws that you have.
Measure the length of the junction box, and mark on the mounting screw with a permanent marker where you need to cut the screw down to size. Then, use a wire stripper to cut the screw. Place the screw in the right threaded hole on the wire stripper, and squeeze the handle tightly to cut the screw down to size. Don't use a hacksaw to cut the screw down to size; it could easily ruin the threads on the screws.
If you don't feel comfortable changing out your light fixture yourself, then contact a residential electrician for assistance.