Browse a typical DIYer’s to-do list and chances are you’ll find an entry reading “Fix lamp.” If the lamp in question is a rehab project stored in the basement, it can wait. But if it’s in use and behaving erratically, unplugging it is your top priority. Failed or flawed lamp wiring is a leading cause of fires in the home. So don’t use it until you fix it.
No matter what the circumstances, learning the basics of lamp repair is a money-saving skill that you’ll use time and again. Although it is simple in theory and often in practice, in some cases it can try your patience. The two aspects that cause the most frustration are locating replacement parts and making new wires fit into the old spaces. If you can overcome these twin obstacles, the rest of the project is a snap.
Components of lamp wiring
The primary electrical components of a lamp are the plug, wires and socket. Each is susceptible to failure. Cords become frayed, plugs lose their snap, sockets crack and connections between the parts break or loosen. You can treat each of these problems as it occurs, but it’s better to overhaul all of the wiring components while you have the lamp disassembled.
Plugs come in many shapes, sizes and configurations. Some are molded directly into the lamp cord, and others are attached with screw terminals or by crimping. It can be dangerous to replace a plug with one that is not an exact match for the original. Bring the old plug along when shopping for a replacement. If you can’t find an exact match, ask an electrical supply professional to help you find a suitable replacement.
LAMP PLUGS: (A) a snap-together plug with a hinged top, (B) a snap-together plug with an insert and a housing, (C) a snap-together plug with a sliding end cover, (D) a screw-connect plug with a rubber housing, (E) a screw-together plug with a plastic screw.
Lamp cords are usually 18-gauge wire made up of braided strands of fine copper. Most do not have a ground wire. Wire that does not have a premolded plug can be purchased in repair kits or by the foot. For an old lamp, you can find reproduction lamp cord at lighting stores or electrical supply stores.
LAMP CORDS: (A) black plastic with a molded plug, (B) white plastic with a molded plug, (C) black “zip cord,” (D) white ”zip cord,” (E) reproduction cord with brown cloth wrap, (F) reproduction cord with gold cloth wrap, (G) black three-wire cord with ground, (H) white three-wire cord with ground.
Sockets vary greatly in construction and quality. The most inexpensive have a lightweight metal housing with a cardboard insulator. Plastic socket housings are inexpensive, too. Because plastic doesn’t conduct electricity, these housings don’t require an insulator. Porcelain sockets cost more but are safe and typically more attractive. They’re vulnerable to cracking, however, so treat them gently.
LAMP SOCKETS:(A) a snap-in-style porcelain socket with torsion springs, (B) a porcelain socket with mounting screws, (C) a switched socket with a set screw for threaded tube connection, (D) an adjustable-height socket with cardboard insulation and a switch, (E) a screw-on socket that threads directly onto hollow threaded tube.
Though the repair process is relatively simple, it’s essential to follow these safety precautions:
- Make sure the lamp is unplugged before you begin.
- Watch out for loose wires when making connections. The fine, braided lamp cords resist neat connections, exposing a strand or two that can contact the socket and cause a short circuit.
- Don’t overstuff the socket base. The cord ends should be trimmed so they’re just long enough to make the socket connections with a little slack between the cord knot and the socket.
- Be careful when fishing wire. Threaded rod ends are sharp enough to slice or strip wire sheathing as it’s pulled through. If the rod openings aren’t protected with washers or bushings, wrap electrical tape around the insides of the opening before inserting new wire.
How to rewire a lamp
With the lamp unplugged, remove the harp; then disconnect the old socket at the base. Disassemble the socket by squeezing the socket shell at the point where it joins the socket base (photo 1). Some shells have the word “press” printed on them to help you identify the correct spot to squeeze. Disconnect the lamp cord at the switch-terminal screws; then pull the cord back through the socket base. You may need to loosen a set screw in the base or untie a knot in the cord to remove it.
Unplug the lamp, remove the harp and disconnect the old lamp socket.
Cut off the plug. Expose some wire on the ends of both cords; then loop and crimp them together. Wrap the cord ends with electrical tape, keeping the connection as narrow as possible (photo 2). Then, fish the new cord up through the hollow threaded rod by pulling upward on the old cord (photo 3). If the new cord does not have an integral molded plug, either attach the new plug end or tie a loose knot in the end so you don’t pull it too far into the tube.
Crimp the new cord onto the old cord so it can be fished through the threaded rod.
Pull the old cord out, drawing the new cord up through the rod.
Thread the cord through the base of the new socket. Expose fresh wire by trimming the ends and then stripping 1/2 in. of insulation from each wire. Tie a loose knot (called an underwriter’s knot) in the cord to keep it from slipping out through the socket base. Leave about 3 in. of free wire after the knot. Twist a loop into the end of each wire with long-nose pliers. Then connect the wires to the screw terminal on the new socket (photo 4). The ridged, insulated wire attaches to the silver screw.
Attach a new socket to the end of the new cord.
Assemble the socket and attach it to the lamp neck (photo 5). Slip the insulation and socket shell over the socket; then snap the shell and socket base together securely. Attach the socket and harp retainer to the neck of the lamp (photo 6), insert a light bulb and test. Reattach the harp and lamp shade.
Assemble the socket and attach it to the lamp neck.
Attach the socket and harp by sliding the caps down; then insert a bulb and test it.
How to replace a plug
Snap-together: Cut the cord at the base of the old plug. Thread the cord through the entry hole in the snap-together housing. Spread the prongs to back the contact spurs out of the cord channel; then slide the cord end all the way into the channel (photo, directly below). You don’t need to strip insulation off the cord. Press the prongs together, forcing the spurs to penetrate the cord sheathing and contact the wires (second photo below). Slide the insert into the housing, backing the cord out of the entry hole, until the insert snaps into the housing.
Thread the new cord through the plug housing and slide it into the plug. You don’t need to strip the wire.
Press the prongs together to drive the spurs into the wire sheathing. Snap the plug into the housing.
Screw-connect: Feed the end of the cord through the entry hole in the back of the plug. Strip the end of each wire to expose 1/2 to 1 in. of bare wire. Tie the insulated wires into a loose knot and cinch the cord by tugging lightly against the plug (photo directly below). Twist loops into the ends of the wires with long-nose pliers; then attach the wires to the screw terminals inside the plug (second photo below). If the plug is polarized, the ridged half attaches to the wider plug side. Make sure all of the fine strands are tucked securely under the screw head. Tug gently on the cord to pull the excess cord wire out the back. Slide the plastic screw protector over the prongs and you're done.
Feed the new wire into the plug and tie a loose knot in the stripped wires.
Attach the wires to the plug terminals then insert the plastic protector into the plug.