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Understanding your repairs - Capacitors

Understanding your repairs - Capacitors

A capacitor is a small cylindrical object that can store energy within an electrostatic field and is one of the key parts of the electrical system in an air conditioner. Without capacitors, the motors that power the compressor and fans will not work.

Start capacitor, run capacitor, single capacitor, dual capacitor, Run Cap – 5, 10, 12.5, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 7.5, Dual cap

Attached to motors, the start capacitor sends a jolt to power up the motor and the run capacitor stays on sending a regular series of jolts to keep the motor working. The motors that capacitors work with are the compressor, blower motor, and outside fan.


Single capacitor  – Start capacitor and run capacitor separately.

Dual capacitor  – a combination of start and run capacitors in the same casing.

Due to the great deal of electricity that flows through capacitors, they can become extremely hot and when temperatures rise the components generate even more heat and often fail. Even just excess power can wear the capacitor down to a point where it can no longer hold a charge.

As a capacitor begins to fail, you will usually hear a clicking sound from within in the cabinet. When a run or start capacitor no longer works, the motor it’s attached to will hum but not start. If this is not fixed the motor can burn out and require a full replacement.

Weakening capacitors connected to the compressor will lead to a condition called “hard starting,” where the AC will struggle to turn on and then shut off again soon after. This places immense strain on the compressor and the other parts of the AC.

In most cases, we will replace the capacitors that are risking the operation of the air conditioner. You should never attempt to do the replacement on your own since the oil that leaks from broken and damaged capacitors is often dangerous to handle.

Although the electrical system needs the most repairs of any part of an air conditioner, you can still prevent most of these repairs through a system of regular maintenance.