Are AC capacitors universal? While we may not think much about the inner workings of our AC unit, understanding the role of capacitors can help us better maintain and troubleshoot any issues that may arise. As we all know, air conditioning is an essential part of our daily lives, especially in sunny Southwest Florida. So, let’s explore whether or not AC capacitors are universal and what that means for your cooling system.

What are AC Capacitors?

An AC capacitor is a passive electronic component that stores and releases electric charge in an alternating current (AC) circuit. It consists of two conducting plates separated by an insulating material known as a dielectric. The conducting plates are usually made of metal and are connected to the AC circuit. The dielectric material, which can be made of ceramic, plastic, or paper, prevents the flow of direct current (DC) between the plates, but allows AC to pass through.

An AC capacitor’s job is to store energy to help your AC start up. It’s necessary because your AC takes a lot more energy to start than it does to continue running once it’s started. So AC capacitors are very important for AC systems to run.

Are AC Capacitors Universal?

AC capacitors are not universal and are specific to the type of AC system. Each AC system is designed with specific voltage, capacitance, and frequency requirements, and the capacitor must match those specifications to function properly.

With that said, the determining factors for whether or not an AC capacitor will work with an AC system are microfarad rating and voltage. If those two factors are compatible, the AC capacitor will work regardless of the other specifications. It’s important to consult the manufacturer’s specifications or contact professional AC techs to ensure the correct replacement capacitor is used for any AC system.

Different Types of AC Capacitors

Did you know there is more than one capacitor in your AC unit? There are four different types of capacitors and they all have different jobs.

Compressor Motor Run Capacitor

This capacitor is connected to the compressor motor and provides the necessary electrical energy to keep the compressor running in your outdoor unit. It helps the motor to maintain a constant speed and avoid overheating, and also helps start the motor when the unit is turned on.

Indoor Fan Motor Run Capacitor

This capacitor is connected to the indoor blower motor and helps the fan to maintain a constant speed while circulating air throughout the indoor space. It also helps the fan to start when the AC unit is turned on.

Outside Fan Run Capacitor

This capacitor is connected to the outside fan motor and helps it maintain a constant speed while pulling air through the AC unit’s condenser coils. This fan helps to dissipate heat from the refrigerant, allowing it to cool and become a liquid.

Start Capacitor

This capacitor, also known as the AC run capacitor, is responsible for providing the initial jolt of electricity needed to start the compressor motor. It is usually larger than the run capacitors and is only used for a short period of time, typically only a second or two.

Without these individual capacitors, the various motors in an air conditioning unit would not be able to function properly, causing the AC unit to malfunction or fail altogether. Regular maintenance and replacement of these components will be necessary throughout the life of your AC unit.

What’s the Difference Between Single and Dual Run Capacitors?

Another decision you’ll run into when preparing for an AC capacitor replacement is choosing between single and dual-run capacitors. Single and dual-run capacitors both help in the start-up and operation of the air conditioner’s compressor motor. While both single and dual run capacitors serve the same purpose, they differ in their design and functions.

1. Design

Single run capacitors contain two terminals and have a single capacitance value. They are cylindrical in shape and are smaller in size. On the other hand, dual run capacitors have three terminals and two capacitance values. They are usually oval or round in shape and are larger in size compared to single run capacitors.

2. Function

The main function of a single run capacitor is to provide the necessary power to start the compressor motor of an air conditioning system. They store electrical energy and release it when required, allowing the motor to start smoothly. Single run capacitors have a limited range of capacitance values and are designed for a specific motor size.

A dual run capacitor, on the other hand, has two capacitance values, one for the compressor motor and the other for the condenser fan motor. They perform the same function as single run capacitors but with the added function of starting and running the fan motor. They have a wider range of capacitance values and can be used for different motor sizes.

3. Usage

Single capacitors are typically used in smaller air conditioning units, while dual run capacitors are used in larger units. Since they have the ability to run both the compressor and fan motor, dual run capacitors are commonly used in central air conditioning systems.

4. Cost

Single run capacitors are generally less expensive compared to dual run capacitors due to their simpler design and limited functionality.

The main difference between single and dual run capacitors is their design and functions. The best choice between the two when you need a new capacitor depends on the size and type of HVAC system being used.

Common Symptoms of a Bad Capacitor

Here are some common problems that may point to a bad AC capacitor and signal that you need to call an HVAC professional for AC repairs.

1. AC Unit Won’t Turn On

The most common symptom of a failed AC capacitor is when the air conditioning unit does not turn on at all. This can be because of the capacitor’s inability to supply the necessary electrical energy to the compressor and fan motors.

2. Inadequate Cooling

The capacitor regulates the voltage and provides the necessary electrical energy to run the compressor and fan motors. If the capacitor is malfunctioning, the AC unit may not be able to produce enough cool air to adequately cool the space.

3. Frequent Tripping of Circuit Breaker

A failing AC capacitor can cause the electrical system to overload, leading to frequent power surges, or powerful bursts of electricity, and trips of the circuit breaker. This can happen due to the capacitor’s inability to regulate the voltage properly, causing fluctuations in the electrical system.

4. Loud or Strange Noises

If the AC capacitor is damaged or malfunctioning, it can cause the air conditioning unit to produce loud and unusual noises. This can happen due to a faulty capacitor putting extra strain on the compressor and fan motors, resulting in unusual sounds.

5. Hot Air Blowing From Vents

Another common symptom of a bad AC capacitor is hot air blowing from the vents instead of cool air. This can happen when the capacitor is unable to provide the necessary electrical energy to power the compressor and fan motors, resulting in the AC unit blowing out hot air.

6. AC Unit Turns Off Intermittently

A malfunctioning AC capacitor may cause the unit to turn off intermittently. This can happen when the capacitor is unable to maintain a steady flow of electrical energy to the compressor and fan motors, leading to the AC unit shutting off unexpectedly.

7. Excessive Humidity or Moisture

The AC unit is responsible for dehumidifying the air as well as cooling it. A failing capacitor can cause fluctuations in the moisture levels in the air, resulting in excessive humidity or moisture in the space.

8. Burnt or Swollen Capacitor

In some cases, a failed AC capacitor may be physically damaged and show visible signs of burning or swelling. If you notice any discoloration, bulging, or burning on your AC capacitor, it is likely that it needs to be replaced.

Just keep in mind that some of these symptoms can also be caused by other issues with the AC unit. It is always best to have a professional HVAC technician inspect and diagnose the problem before attempting any repairs.


Getting the right capacitor for your air conditioning unit is important! Contact Dolphin Cooling and we’ll send out a qualified technician to diagnose your AC’s issues and repair the problem promptly. Please note that AC capacitors store high voltage that can cause serious injury. It’s very important to have a trained professional test, diagnose, and repair capacitor issues. Contact us today to schedule and appointment.