Capacitor
Updated
A capacitor is a small cylinder that stores an electrical charge and releases it to help motors start and keep running. Your outdoor AC unit typically has one serving the compressor and condenser fan, and the furnace blower has its own.
Capacitors are one of the most common summer failures because heat is what kills them. The hotter the weather, the harder they work, and the ones already weakened by age give out on the worst possible day. The classic symptom is an outdoor unit that hums but will not start, or a fan blade that only spins if something gives it a push.
Common Questions
What does a capacitor do in an AC system?
The capacitor stores electrical charge and delivers the jolt that gets the compressor and fan motors spinning, then smooths the power that keeps them running. Motors draw far more current at startup than while running, and the capacitor covers that gap.
What are the signs of a bad capacitor?
A humming outdoor unit that never starts, a fan blade that will not spin on its own, warm air from the vents, or a breaker that trips when the AC kicks on all point at the capacitor. It is a quick diagnosis on an AC repair visit with a meter in hand.
Why do capacitors fail during heat waves?
Heat is the enemy. Capacitors sit in the outdoor unit's electrical panel next to the contactor, absorbing summer temperatures while the system runs its longest hours. A capacitor already weakened by age loses the rest of its strength on exactly the day the AC works hardest.
Related Terms
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