Adding a ceiling fan pull string is a simple electrical task for anyone with basic electrical wiring skills. However, if you want to add a pull string to an existing fan that doesn't have a switch, be aware this involves considerable rewiring. If you are installing a new ceiling fan pull string, make sure the switch you purchase comes with detailed instructions. Ask the lighting salesperson if your fan will accomodate a switch as well—some models don't.
As with all electrical repairs or replacements, make sure to shut off the power to the outlet and test it with your voltage tester to make sure the connection is dead before working.
Step 1 - Access the Fan Motor
Switch off the power to the fan circuit. Remove any light fixture or the bottom plate or cap to the fan. This usually involves 3 screws. Test the fan with your voltage tester to ensure that the power is off.
Step 2 - Find the Pull Chain Switch
If you're replacing a broken or existing pull chain switch, it should be right above the pull chain. Depending on the model of fan, it might have 3 or 4 wires leading to or from it.
Step 3 - Remove the Switch
Unscrew the cap that holds the switch to the fan body, and pull the switch out of the recessed hole. You'll notice wires of different colors coming out of the switch. Before you pull out the wires, make a quick sketch of what color wire goes where in the switch. These wires will usually be inserted into pressure terminals. Once you have your drawing done, simply pull the wires out of the terminal.
Step 4 - Add the New Switch
Your new switch may or may not come with existing wires. If it does, simply push the new wires into the terminals where you pulled the old wires out. Refer to your drawing or diagram to make sure you have the colors and terminals correct. If your new switch has no pre-installed wires just insert the wires into the terminal yourself, using your wiring nuts (connectors). Make sure to connect black to black, red to red, white to white etc. All your exposed wire ends should be covered by the nut.
Replace the switch, being careful not to pinch the wires. Insert the pull chain through the side of the fan body (you should be able to recognize this once you have the switch in place) and replace the fan housing, caps and lights.
Step 5 - Test Your Switch
Once you have connected everything, turn the power back on and test your pull string.