A 3-prong dryer cord was the standard for dryers prior to 2000. The National Electrical Code currently requires 4-prong dryer outlets in all new home construction. Existing homes may still use 3-prong outlets.

The switch to a 4-prong outlet was due to a flaw in the 3-prong outlet design. In a 3-prong outlet, the ground and neutral wires are contained in the same prong. This has the potential to allow a current to find its way onto the ground wire.

The 4-prong dryer cord is comprised of two hot wires, a neutral wire and a ground wire. This creates a separate return path for unused current. Dryer cords are usually a maximum of six-feet-long as the code requires that an outlet be close to the connected appliance. 

Check to see if you need a 3-prong vs. 4-prong dryer cord and take that into consideration when shopping for new appliances. In general:

• 3-prong plugs are used for homes built before the year 2000. 
• 4-prong plugs are used for homes built after the year 2000. 

Whether you choose to add professional installation to your new dryer purchase or install it yourself, you must purchase a power cord appropriate for your outlet.

Changing a dryer cord is simple but the project isn’t done frequently by most homeowners. Some tips might be new advice for beginners and others are worth repeating even to seasoned DIY-ers. Use common sense when learning how to change a dryer cord.

• Unplug the dryer cord before working on the appliance.
• Do not plug a dryer cord into a receptacle unless it is properly and completely connected to the dryer. 
• Almost all manufacturers sell dryers without a cord attached, allowing you to select 3-prong vs. 4-prong dryer cord to match your outlet. Be sure to check which type you will need before purchasing your appliance and power cord.
• When removing the access panel or connection screws, using magnetic nut drivers and Phillips-head screwdrivers can save you time by preventing screws from falling inside the machine. You may use hand tools or a power drill fitted with appropriate drivers.
• Always follow the manufacturer’s instructions for how to replace a dryer cord that are included with the appliance parts.

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You must make certain that the appliance is disconnected from its power source before beginning to work on changing a dryer cord.

• Turn the dryer into its “Off” position and unplug the unit.
• Open the access panel where the cord enters the back of the dryer. Keep the screws in a safe place until securing the access panel when the project is complete.
• Use pieces of masking tape to label which colored wire attaches to each terminal inside the access panel. The wires are typically color-coded with a black wire on one side, a white wire in the middle, and a red wire on the other side.

After the terminals are labeled for easier installation of the new dryer cord, you can begin to remove the old cord.

• Loosen the connection screws holding the wires in place on the terminal block.
• Disconnect the ground wire or strap that connects the center terminal to the case.
• Use pliers to hold the strain relief bracket in place while loosening the bracket's screws.
• Remove the old cord.

Feed the loose wires of the new dryer cord through the hole in the back of the unit. Then you can attach the new cord.

Tip: When replacement cord wires are color-coded, simply match the colors of the new cord’s wires to those on the terminal block. Consult the dryer wiring diagram in the user manual.

3-prong cord

• Attach the middle or ground wire to the center terminal, one of the outer wires to the right terminal, and the other outer wire to the left terminal.
• Attach the grounding strap or wire that runs from the center terminal to the dryer case.
• Remove the masking tape labels.

4-prong cord

• Attach the white wire to the center neutral terminal.
• Connect the red wire to the right hot terminal 
• Attach the black wire to the left hot terminal.
• Attach the green wire to the green grounding screw or dryer case.
• Remove the masking tape labels.

Double check that you have firmly tightened the terminal screws that connect the new wires. Now install the strain relief bracket to protect the connections and help avoid a possible short if the cord is yanked.

• Fit the strain relief bracket into the cord access hole.
• Use pliers to hold the bracket in place and evenly tighten both bracket screws firmly to secure the cord.
• Replace the access panel on the back of the dryer.

Before cleaning up and putting away your tools, test the dryer to check your work.

• Double-check that the dryer is in the “Off” position.
• Plug the new dryer cord into the outlet.
• Turn the dryer to the “On” position to test operation.

When satisfied, make sure that your tools are removed from behind the dryer. Then, move the dryer into place.