Air Conditioner

What is the Difference Between a Start Capacitor and a Run Capacitor?

July 21, 2019

The air conditioner in your Wake Forest, North Carolina, home is composed of many parts. They all have a vital function to perform and they work together to ensure that cool air is delivered into your home. If you suddenly find that the AC unit isn’t working properly, there is a possibility that the start capacitor or run capacitor has failed or gone bad. Let’s look at what capacitors are, their importance in keeping your home cool, and signs that they need to be repaired or replaced.

The Role of Capacitors

The capacitors are an essential part of your air conditioning system. The capacitors are small cylindrical shaped containers that lie inside the housing of the air conditioner. The main purpose of them is to store energy and provide it to the motor upon start-up and when running. They are called a start capacitor and a run capacitor.

Why the Start Capacitor Is so Important

When your air conditioner first turns on, it requires a massive amount of energy to begin its cycle. Often, your home’s electrical system can’t handle the large load of energy needed to get the system going. This is where the start capacitor comes in. Once the AC is turned on, the start capacitor sends an immediate electrical charge, or boost, to get the rotation of the motor started. Once the proper amount of torque, or energy, is pushed to the motor, then the start capacitor shuts off.

The Function of the Run Capacitor

Once the system has started and is operating, the run capacitor takes over and provides the extra power to run the air conditioner for long periods of time. When the air conditioner is running, both capacitors create and store energy for the push for the next cycle. Many air conditioning systems, as well as heat pumps, use a dual capacitor system which connects both the start and run capacitors to the compressor and fan motors.

What Causes a Capacitor to Fail?

As with any other component of your air conditioning system, capacitors eventually wear out and either need a repair or replacement. One of the main reasons a capacitor may fail is due to overheating. They are quite sensitive to heat and if the air conditioner is sitting in full sun, the capacitor can easily overheat.

When the temperatures soar, such as during a heat wave, the AC system may run longer and harder than normal which can also cause electrical overheating. Power surges from a fluctuation in the electrical grid or from an overloaded circuit in your home can also cause irreparable damage to the capacitors. The age of the capacitors can also be a cause of failure.

Having routine preventive maintenance can help to prevent a capacitor from causing complete failure. During maintenance, our technicians can test for a faulty capacitor and replace it before further damage to the air conditioner incurs.

Signs of a Bad Capacitor

Trying to determine if the capacitors are bad is something best left to our professionally trained technicians. However, there are signs that might alert you to the problem. If the compressor on the outside unit of your air conditioner has trouble starting or cycles quickly on and off, the start capacitor may be failing. If the air conditioner repeatedly starts and stops, the run capacitor might be the culprit. If you hear an unusual clicking sound coming from the inside cabinet of the air conditioner, the capacitor is probably failing.

If the AC is running, yet there is no cold air coming out of the vents, then the fan motor isn’t working properly. If the air conditioner won’t turn on at all, the capacitor doesn’t have the capability to send enough power to start the motor.

Don’t ignore any of these signs of trouble! If the motor, compressor, and fans are not receiving the power they need to run efficiently, the entire system will eventually break down, resulting in expensive repairs or even an entire system replacement.

Don’t hesitate to call our experts at Cape Fear Air Conditioning, Heating, & Electrical Company, Inc. right away if your air conditioner needs a repair. You can reach us at 919-246-5801.

Image provided by iStock

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