If the cord to your space heater, coffeemaker or any other appliance gets damaged, you should replace it rather than trying to repair it. A cord with severed or partially melted insulation won't ever be really safe, no matter how well you make the repair. This is also true for extension cords.
To replace a cord, you'll need to disassemble the appliance to access the cord terminals, and you'll need a replacement cord that is the same gauge as the existing one. If only the plug is damaged, you may be able to replace it without having to replace the entire cord, but the plug must be rated for the current load of the appliance.
Test the Cord
Sometimes a cord that appears to be in good shape has internal damage that may be affecting the operation of the appliance. There's an easy way to test it.
Things You'll Need
- Disassemble the appliance to uncover the cord terminals.
- Disconnect the cord by desoldering it with a soldering iron or loosening the terminal screws with a screwdriver.
- Twist the wires together, then clip the leads of a multimeter onto the plug prongs. Set the meter to read ohms of reisistance (Ω).
- If the cord is good, the display should read 0, but double-check by crimping the cord at various places along its length and watching the meter. Any fluctuations in the reading indicate internal breaches and that the cord needs to be replaced.
Buy a New Cord
Most appliance cords are 14- or 16-gauge, but some high-demand heaters have 12-gauge cords. It's unlikely you'll ever have to replace a cord on a heavy-duty, 240-volt appliance, such as a stove, but you can do it. For a stove, the cord you buy should be 6-, 8- or 10-gauge and identical to the cord you're replacing.
Keep in mind that, if the cord you're replacing has a plug with a ground prong, you need a ground prong on the new one, as well. Similarly, if the plug on the existing cord has two prongs with slightly different sizes, this means that it's a polarized cord. Be sure the replacement cord has the same type of plug.
Replacing an Electrical Cord
Many appliance cords are soldered to the terminals, but you can't tell until you disassemble the appliance and uncover the terminals. If the connections are soldered, you'll need a soldering iron and silver solder, which is available at any hardware store or building supply outlet.
Things You'll Need
Multi-driver or hex wrench set
Step 1: Disassemble the Appliance
Depending on the appliance, you may be able to access the cord terminals by removing the bottom or a panel on the back. In some cases, however, more extensive disassembly may be required. Look up the manual for the appliance on the manufacturer's website and download a schematic diagram so you'll know where everything goes when it comes time for reassembly. Besides the diagram, the only other tools you'll need for disassembly are a multi-driver or hex wrench.
Step 2: Disconnect the Old Cord
Loosen the terminal screws with a screwdriver if the wires are connected to screws. If the wires are soldered, touch a hot soldering iron to each terminal to melt the solder. When the solder liquifies, pull the wire off. Pull the old cord out of the appliance and discard it.
Step 3: Prepare the New Cord
Separate the wires on the end of the new cord. If they aren't already exposed, cut off about 2 inches of cable sheathing, using a utility knife, and remove insulation from the wires using a wire stripper. Note which wire is hot, which is neutral and which is ground. Depending on the cord, there are three ways to tell:
- If the cord has a ground prong on the plug and the individual wires are covered with insulation, the black wire is hot, the white wire is neutral and the bare or green wire is ground.
- If the cord is not grounded, but it has a polarized plug, the neutral wire will have ribbing, texture, or a white stripe on the plastic insulation jacket on the cord. . This half of the cord will lead to the wider of the two prongs on the cord plug. The hot wire has no markings and will lead to the narrower prong on the cord plug.
Step 4: Connect the Hot Wire to the Brass Terminal
Feed the new cord into the terminal area and isolate the hot wire. If the terminals have screw connections, wrap the hot wire clockwise around the brass screw and tighten the screw down with a screwdriver. If the terminals have solder connections, wrap or twist the wire onto the brass terminal and solder it in place.
Step 5: Connect the Neutral and Ground Wires
Loosen the screw on the silver-colored terminal, wrap the neutral wire clockwise around it and tighten it down. If the cord has a ground wire, connect it to the green terminal screw. If the connections are soldered, use the soldering iron to make the connections.
Step 6: Finish Up
Reassemble the appliance, then plug in the appliance and test it.
Replacing a Cord Plug
Sometimes, the only thing wrong with a cord is that the plug has been damaged. One of the prongs may have broken off, or the plug may have overheated and melted. You can often just cut off the damaged plug, strip the wires on the end of the cord, and install a new plug. Be sure the plug you use is sized for the wire gauge of the cord.
The procedure is similar to connecting a new cord to an appliance, except instead of disassembling the appliance, you disassemble the plug by loosening a screw or pulling the core out of an outer jacket to expose the screw terminals.
- Remove the plug core from the outer jacket. Slide the cord through the hole in the outer jacket before connecting it to the screw terminals on the plug core.
- Connect the hot wire to the brass terminal on the plug core. If the screws are the same color, the hot prong will be the one that is the narrower of the two.
- Connect the neutral wire to silver-colored screw terminal. If the screws are the same color, the neutral prong will be the one leading to the wider prong.
- If there is ground wire, attach it to the green ground screw on the plug.
- After all wires are connected, slide the core back into the outer jacket and secure it tightly. Some plugs are held together with screws, while others simply snap into place.
- Test the appliance to make sure it operates correctly.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.