Extension cords can be damaged in many different ways, from dragging them along the ground to running over them with vehicles or closing them in a door. Perhaps the most common damage comes from pulling out the plug by the cord—not the plug. Eventually, this stretches out the cord wires and separates the sheathing, or outer jacket, from the plug, exposing the cord wires. One more result of wear and tear is the ground prong coming loose. When any of these forms of damage occur, it's time to replace the plug.
Repairing Extension Cords
Replacing a plug is the only repair you should ever make to an extension cord. Cords with damaged sheathing, exposed wires, or other damage to the cord itself should be replaced or cut off to a point where the bad section is eliminated and a new plug is added to the shortened cord. Just wrapping the damaged cord with electrical tape isn't good enough. You don't know how much damage the cord has suffered, and electrical tape provides unreliable protection against shock.
Extension cords come in many forms, as do the replacement plugs used to fix them. Make sure to choose a plug that is suited for the cord—a grounded three-prong plug if the cord has a ground wire, a two-prong polarized plug for simple household extension cords, etc.
The project demonstrated here shows how to replace the plug on a typical medium-duty grounded extension cord.
Equipment / Tools
- Wire cutters
- Utility knife
- Wire strippers
- Phillips screwdriver
- Replacement plug
Cut Off the Old Plug and Fit the New
Make sure the cord is unplugged from any power source. Cut off the old plug from the cord, using wire cutters. Cut off any damaged portion at the end of the cord. Slide the new plug over the cut end of the cord and out of the way for now.
Some plugs have two parts, with one piece containing the wiring connections and prongs and another piece that is an outer shell or body. In this case, slide only the outer shell onto the cord for now.
The replacement plug must have the same amperage and voltage ratings as the original cord. These ratings are printed on the plug. The ratings on the old plug will indicate the type you need.
Strip the Outer Jacket
Cut partially through the outer jacket of the cord, using a utility knife. You must be careful not to cut all the way through the jacket because you may also cut through the insulation on the cord wires, creating a serious shock or fire hazard. The cut should extend 3 inches from the end of the cord.
Split the jacket with your fingernails (at the end of the cord) and peel the two sides apart along the cut. Trim off the loose jacket with wire cutters or a utility knife.
Strip the Wire Insulation
Strip about 3/4 inch of outer insulation from the end of each conducting wire inside the cord, using wire strippers. Use the notch on the strippers that precisely matches the diameter (gauge) of the wire.
Tie an Underwriter's Knot
Tie the white (neutral) and black (hot) cord wires into an underwriter's knot, if there is room for the knot inside the cord body. This provides added protection against the cord wires separating from the plug connections if the cord is tugged. If there isn't enough room for an underwriter's knot, it's okay not to make one, as long as the plug has a clamping device for securing the cord.
Connect the Cord Wires
Using a screwdriver, loosen the terminal screws on the plug. Wrap the bare end of the black (hot) wire clockwise around the brass terminal. Many new plugs have slots to insert the wire. Tighten the screw down onto the wire. Make sure that no stray wires are sticking out from the connection. Wrapping the wire clockwise ensures that the wire loop tightens around the screw as the screw is tightened.
Connect the white (neutral) wire to the silver terminal, and connect the green (ground) wire to the ground screw, using the same technique. The ground screw may be marked with green coloring, but in any case, it is always connected to the U-shaped ground prong on the plug. Double-check the connections for tightness by pulling gently on each wire.
The new male or female plug will usually have an indicator line on it to show how much insulation to strip for an optimum connection. Most newer plugs have a clamping connection that the wire slides straight into before tightening the screw. This eliminates the need for wrapping the bare wire around the screws.
Secure the Plug
Using a screwdriver, tighten the plug clamp onto the cord. If the plug is in two parts, slide the outer shell up to the wired portion of the plug and join the two parts with the provided screws, then tighten the cord clamp on the body.