A ceiling fan capacitor is a small component in the fan's switch housing that stores and releases electrical charge to create the phase shift a single-phase induction motor needs to start and run at each speed. Rated in microfarads (µF) and volts, a failing capacitor causes slow spinning, humming, a fan that will not start, or missing speeds.
Why it matters to you
A fan that hums but will not start, spins slowly on high, or has lost one speed setting often needs only a capacitor rather than a new fan.
Practical guidance
Turn off power at the circuit breaker, not just the wall switch, before opening a fan's switch housing, and confirm it is dead with a non-contact voltage tester. A replacement must match the original's microfarad ratings and wiring exactly, and a fan that wobbles hard should not be used until its mounting is checked.