Fix a Lamp Cord

Follow the rules of polarity for a safe fix

Replacing a damaged plug is easy, but for safety you have to follow proper wiring rules, especially when wiring a polarized plug. A polarized plug has one wide and one narrow blade.

By the DIY experts of The Family Handyman Magazine

Step 1: Buy a polarized replacement plug, if needed

Damaged plugs and nicked, frayed cords are a safety hazard and need to be replaced. Putting a new plug on is straightforward, but there are a few basic rules.

To prevent shocks from the metal parts of a light, lamp cords and two-wire extension cords are always polarized. This means the plug has a small blade for the hot wire and a wide blade for the neutral wire, and the wires feeding those blades should not be reversed when you put a new plug on. Always use a polarized plug for a lamp, extension cord or any other cord that’s polarized to begin with. Don’t ever use a nonpolarized replacement plug with same-size blades to replace a polarized plug. (Nonpolarized plugs are often found on double-insulated tools and some appliances.)

Step 2: Identify the neutral wire

You can identify the neutral side of the wire just by looking for markings on one of the wires. The most common identifier is ribbing in the rubber insulation all along one edge, but it can also be a white wire or a white stripe (photo below).

How to Identify the Neutral Wire

To identify the neutral wire look for the markings shown in the photos.

Polarized cord
Polarized cord
Polarized cord
Cord not polarized

Step 3: Wire the new plug

To prepare the cut end for a new plug, cut or pull the two sides apart, then strip off about 3/4 in. of insulation (Photo 1). Lamp and extension cords are usually 18 gauge, but if you’re not sure, strip the wire through the 14- or 16-gauge slot first. If it doesn’t strip cleanly, try the next gauge. Note: Stranded (“STRD”) wire gauges are marked on the left, solid gauges are marked on the right.

Twist the strands of wire tight, then fasten them into the replacement plug with the neutral on the wide-blade side (Photo 2). Then snap or screw the plug back together.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • 4-in-1 screwdriver
  • Wire stripper/cutter

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • New plug

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