Ceiling fans with pull chains can be toggled between different speeds. Multi-position pull chains cycle the fan between two to four speeds, often termed "off," "low," "medium" and "high." Some pull chains work as a simple on/off switch and generally link to the fan's lighting section. Your ceiling fan may have two pull chains, or just the one if there's no light fixture.
The pull chain feeds up into a switch located in the switch housing. The housing is generally quite small, about the size of a silver dollar. Wires connect to the chain itself via wire nuts, or directly to the chain. The wires are each a different color and, depending on the ceiling fan's capability, there may be as few as two or as many as six. As the chain is pulled, it switches to the different wires and controls the speed of the motor that turns the fan.
Problems can occur when the chain itself breaks apart. When pulled too hard or too often, the chain can break away from the socket or crack the plastic parts inside the mechanism. Additionally, the chain can become misaligned in the channel, or it may just need a little lubrication to run smoothly. Occasionally, the mechanism simply separates from the fixture from repeated stress.
Cut the power to the fan by turning off the appropriate breaker. Remove the switch housing and unscrew the pull chain. Loosen the wire nuts with needle-nose pliers and gently detach the pull chain assembly. Note where each color of wire is attached to the assembly. Replace the assembly with a new pull chain unit, and reattach the wires in the order they were originally. Screw the switch housing back into place and test the pull chain to ensure it works.