To connect a new four-prong electric dryer wiring plug, attach the green wire of the cord to the green grounding screw or dryer case of the machine with a magnetic screwdriver. Secure the white wire to the center terminal, and attach the red wire to the right terminal. Attach the black wire to the left terminal. In most cases, the manufacturer color-codes the wires of the dryer cord to match the terminals on the dryer.
Place the strain relief bracket around the cord along the cord access hole. Tighten the nuts on either side of the bracket evenly until the brackets fits securely on the cord. Don't skip this step because the strain relief bracket prevents the dryer from shorting out and stops undue stress from affecting the terminals of the cord. Then, replace the electrical connection cover plate that covers the cord terminals by screwing it into place.
To replace an old dryer cord with a new one, start by unplugging the dryer and rotating it so you can clearly see the back panel. Remove any screws holding the electrical connection cover plate over the electrical terminals where the dryer cord attaches to the machine. Remove the screws on the connection terminals and the strain relief cord bracket, and then pull out the old dryer cord. Then proceed to install the new cord.
Older dryers may have a three-prong electrical cord, which only uses three wires. Newer homes are built with four-prong electrical sockets, but you can still use your old dryer by replacing the old three-prong cord and installing a new four-prong cord.