Extension cords are a must for any homeowner. They are needed to temporarily extend power to tools and lighting inside and outside of your home. On occasion they will wear out, break or get cut and need repair. Extension cords are expensive to replace these days, so to save some money you can just repair it yourself.
Replacing either the male or female end of the cord is quite simple, you can pick up a new end at your local hardware store for a few dollars and have your cord safely back in service in about 5 min. If your cord is broken in the middle,
Technically, you’re not supposed to splice extension cords. Even if you solder the wires, wrap each wire with electrical tape and encase the whole splice in heat shrinkable tubing, it still won’t have the abrasion resistance of a new cord. Plus, it’s not permissible under the National Electrical Code.
Instead, if both sections are long enough to be worth saving, just buy a high-quality plug and receptacle and make two cords out of one. Be sure the new ends are rated to carry the same load as the old cord and that both have built-in strain relief clamps. Otherwise, just buy one end and accept the fact that your 100-ft. cord is now only 92.56 ft. Family Handyman
This video is a quick guide on replacing the end of your extension cord.
Remember for your safety only use extension cords for temporary power, if you are installing something permanent, install a new outlet in that location.