Installing a Fixture Box

A self-supporting retrofit box can be installed in an existing ceiling or wall if your light fixture doesn’t have a box. This regularly will be the case with very old wiring or poorly done additions to your electrical system. You’d be surprised how many old incandescent fixtures are attached directly to plaster lath instead of to any kind of box. Retrofit boxes come in two flavors: metal and plastic. Each is designed to fit snugly against either plaster or drywall by using adjustable ears and brackets that expand and/or tighten against the wall. A plastic box has an attached, U-shaped bracket that tightens like a toggle bolt as its attachment screw is tightened. A metal retrofit box comes with brackets or supports (known as “Madison Holdits” and sometimes as “battleships”) that fit between the box and the wall. As they are pulled out, they firm up the fit of the box. The arms of the supports are then bent over the edge of the box, tucked inside, and pinched tightly with pliers.
Another version of a metal retrofit box features a screw-operated support on each side of the box. As the screws are tightened, the metal support wedges the box in tightly against the plaster or drywall. A retrofit plastic box has plastic or metal internal cable clamps that help secure the cables to the box should it ever slip from the opening. Metal boxes are a bit trickier to use if you’re unfamiliar with them, so consider using plastic retrofit boxes for your work.

Time to Replace

Installing new fixtures is a doable homeowner project. It’s easier to do with modern wiring and boxes, but it still can be done with older types of wire as well. To replace a fixture, follow all safety precautions, read the instructions and diagrams that come with the fixture, and …

1. Turn the power off and test to make sure it’s off.
2. Follow the preceding steps for testing the fixture’s socket to remove the fixture and undo the wire connections.
3. If the fixture does not have an electrical box, install .
4. Install the mounting strap that comes with your new fixture to the box. (The strap, also called a mounting yoke, has predrilled holes set to the dimensions of the fixture.)
5. Connect the black wire and the white wire from the fixture to their counterparts in the circuit wires.
6. Connect the grounding wire to the grounding screw on the mounting strap and to the grounding conductor that might come attached to the fixture.
7. Install a light bulb, turn on the power, and test the fixture. After the test, turn off the power and remove the bulb.
8. Attach the fixture with its mounting screws to the mounting strap.
9. Install the light bulb and the globe.

Inspect First

There are two main reasons for replacing a light fixture:

• It isn’t working, and you believe it is somehow broken.
• You want to install an updated style or a fixture that will offer more light.

You should do a number of checks before pronouncing a light fixture broken or beyond repair. You already know about checking the switch and the fixture itself for power. In addition, you should look at the following:

• The lamp (light bulb)
• The socket
• The wire connections inside the box

Checking the light bulb is the obvious first course of action—replacing the bulb with one that’s working. If it got jostled around in a storage drawer or even on the way home from the hardware store, there’s always a chance a new bulb isn’t working, so check it in a fixture or lamp you know is working. The next thing to check is the socket. At the bottom of the socket is a small metal tab that makes contact with the bottom of the lamp. Turn the power off and check with your voltage tester by placing one probe on the metal tab and one on the inside of the metal socket. The bulb should not glow. If it does, the power is still on, and you need to shut off the correct circuit. With the correct circuit shut off, test the fixture again with your voltage tester. With the power off, pull the end of the tab up a little bit using the end of a screwdriver. Screw in the lamp, turn on the power, and try the fixture again. These tabs sometimes become depressed or flattened out and don’t form a tight contact with the lamp. Why would the contact suddenly be broken? All it takes is a slight vibration in the fixture from, say, a large truck passing by. If a light bulb that you know is good doesn’t work, you have a problem with the socket. Remove the fixture to test the socket by following these steps:

1. With all glass globes, lampshades, and light bulbs removed, unscrew the fixture from the box by turning the mounting screws counterclockwise.
2. Carefully pull down the fixture and let it rest on top of the ladder. This is critical if it’s a heavy fixture.
3. Disconnect the wires from the terminal screws and take down the fixture.
4. Attach the continuity tester’s clip to the hot wire terminal screw, and place the probe against the metal tab in the socket. If the tester does not glow, the socket needs to be replaced.
5. Attach the continuity tester’s clip to the neutral terminal and the probe to the threaded portion of the socket. Again, if the tester’s bulb does not glow, the socket needs replacement.

Some sockets are permanently attached to the fixture, in which case the entire fixture must be replaced. Others are attached to the fixture with screws and can be removed and replaced. Take your old socket to the hardware, lighting, or electrical-supply store and purchase an identical replacement.
The same vibrations also can cause the wire connections to come loose just enough to lose contact with the fixture.