Sometimes wire insulation gets damaged. The wire will still work, but exposed metal increases the risk of short circuit, electrical shock, or even fire. When you come across damaged insulation, you really need to fix it. Here’s how to repair wire insulation.
The easiest and cheapest option is to just wrap some vinyl electrical tape around the damaged insulation to shore it up. This works, but it doesn’t look professional. Then again, who’s ever going to look there? To me, the bigger downside besides appearance is that the adhesive will deteriorate over time. It will take years, but it’s not something I would consider a permanent repair.
Liquid electrical tape
Home improvement stores sell a polymer compound they call liquid electrical tape. Brush it onto the exposed wire, and it will bond with the surviving insulation and harden into a rubbery mass. It yields a more permanent repair, and if you’re careful, it looks more professional too. The downside is the cost, but a bottle of liquid electrical tape will do a large number of small repair jobs.
Heat shrink tubing
The most professional repair involves heat shrink tubing. As long as you can disconnect one end of the wire, you can simply slip a piece of tube over the wire, reconnect the other end, and then apply a heat to the tube with a heat gun or even a common hair dryer. The tube will shrink down and grip tightly onto whatever remains underneath. For really professional-looking results, you can even get colored heat shrink tubing that matches common wire colors. Home Depot is one source.
You may have to de-solder and re-solder some wire to use this method. Here’s some advice on soldering.
If the insulation is too far gone, it might be cheaper and/or easier to just replace the wire altogether with new wire. This may involve soldering, but read my piece on soldering I linked to above. It’s not as hard as it sounds.