Check the bulb first!
When a lamp flickers or doesn't light up at all, chances are that one of the parts has gone bad. Here we’ll show you how to replace all the key parts. But don't overlook the obvious: no power or a bad bulb. Try a new bulb and plug the lamp into a different outlet before taking things apart.
If that doesn't work, operate the switch. It should turn on and off without flickering. Next, unplug the lamp and inspect the cord and plug. If you can't find any obvious problems, replace all the electrical parts. It only takes a few more minutes than replacing just one, and the cost is minimal.
Pull the plug before working on a lamp.
Replace a faulty socket
A lamp socket itself can go bad, but more often it's the switch inside the socket. Either way, the solution is replacement. A new socket is inexpensive. Regardless of the existing switch type, you can choose a push-through switch, a pull chain, a turn knob or a threeway turn knob that provides two brightness levels. You can also choose a socket without a switch and install a switched cord instead.
The old socket shell is supposed to pop out of its base with a squeeze and a tug, but you might have to pry it out with a screwdriver (Photo 1). The socket base can be stubborn too. It’s screwed onto a threaded tube that runs down through the lamp’s body. When you try to unscrew it, you might unscrew the nut at the other end of the tube instead. This will allow the parts of the lamp body to come apart, but that isn’t a big problem. Just use pliers to twist the base off the tube (Photo 2), reassemble the lamp body and screw on the new socket base to hold it all together.
When you connect the new socket, don't reuse the bare ends of the wires. Some of the tiny strands of wire are probably broken. Cut them off and strip away 1/2 in. of insulation with a wire stripper (Photo 3). Using a wire stripper is almost foolproof, as long as you choose the correct pair of notches to bite through the wire's insulation. Most wire strippers are sized for solid wire, rather than the slightly larger stranded wire used in lamp cords. You can get around this problem by using the next larger pair of notches. Since most lamp wires are 18 gauge, start with the notches labeled 16. If the stripper won't remove the insulation, use smaller notches. If the stripper removes strands of wire, cut off an inch of cord and start over using larger notches.
When you connect the wires to the new socket, the neutral wire must connect to the silver screw (Photo 4). To identify the neutral wire, start at the plug. The wider plug blade is connected to the neutral wire, and you'll find that the neutral wire is distinguished from the “hot” wire. The two wires may be different colors, there may be printing on one or the other, or there may be tiny ribs or indentations in the plastic covering the neutral wire. If your old plug blades are of equal width, replace the plug and cord along with the socket.
Replace a cracked cord
The insulation on cords becomes stiff and brittle as it ages. Eventually, it cracks and might even flake off the wire, creating a shock and fire hazard. Don't try to solve this problem with electrical tape. Replace the cord. Cord replacement is also the best fix for a bad cord-mounted switch. You can buy a cord that has a switch attached.
Save yourself some time by buying a cord that's already connected to a plug. Lamp cord sold at home centers and hardware stores is usually 18 gauge. That’s large enough to handle 840 watts of lighting. If you have one of those rare lamps that uses bulbs totaling more than 840 watts, have it fixed at a lamp repair shop. Make sure the cord is protected by a screw-on bushing where it enters the threaded tube and by a plastic or rubber grommet through the lamp body (Photo 1). Without a bushing or grommet, sharp edges can cut into the cord's insulation. If you can’t find a bushing or grommet the right size at a home center or hardware store, you'll find multiple sources online.
To replace the cord, you'll take most of the socket replacement steps shown above. Remove the socket from its base, cut the old cord and pull it out. Feed the cord up through the threaded tube in the lamp's body (Photo 2). Then connect the new cord to the socket. Most cords come with the ends already stripped, so you won't even need a wire stripper.
Replace a problem plug
Plugs on lamp cords often have a weak point where the cord enters the plug. Pulling and flexing can break the wires at this point, leaving you with a lamp that flickers when you jiggle the cord. The cure is to replace the plug. To do this safely, choose a polarized plug. A polarized plug has one blade that's wider than the other so it fits into an outlet only one way. Before you buy a plug, take a close look at the cord. Along with other labeling, you should find “SPT-1” or “SPT-2.” This refers to the thickness of the cord's sheathing, and the plug you buy must have the same listing so it will fit over the sheathing. If you can't find the SPT listing, replace the entire cord as shown above.
The plug you buy may not look exactly like the one shown here, but installing it will be similar. Be sure to read the manufacturer's instructions. When you split the two halves of the cord (Photo 1), be careful not to expose any wire. If you do, cut back the cord and start over. Strip the wire ends and make connections (Photo 2). The neutral wire must connect to the wider blade. If you're not able to identify the neutral wire, replace the entire cord.
Figure A: Anatomy of a Lamp
Figure A shows the parts and assembly of a typical lamp.