Plain-language explanation: This page is educational and does not replace testing the actual equipment.
What a capacitor does
Capacitors store and release electrical energy to create the phase shift needed by many single-phase motors.
Common symptoms
Symptoms can include humming, delayed starting, a stopped outdoor fan, a compressor that will not start, intermittent operation, or a visibly swollen capacitor.
Why a failed capacitor matters
A weak capacitor can increase motor stress and current draw. Continued operation may damage the motor or compressor it supports.
Safety warning
Capacitors can retain an electrical charge after power is disconnected. They should be tested and replaced by someone trained to work safely around electrical equipment.
Frequently asked questions
Can a capacitor fail suddenly?
Yes. Some fail abruptly, while others gradually weaken.
Can a bad capacitor damage a compressor?
It can contribute to hard starting, overheating, and repeated protective shutdowns.
Is a swollen capacitor always bad?
A swollen or leaking capacitor should be considered failed, but some failed capacitors show no visible damage.