What Are the Major Parts of an Air Conditioner?

Air Conditioner

Most people know they have an air conditioner and think the unit sitting outside is it. While this is certainly part of the system, it is only one part of a larger system.

Like most mechanical systems, your air conditioner will eventually need repairs. When you experience problems, it can cause momentary panic, with the stress of large repair bills looming. While some repairs certainly can be costly, the fear is actually based on the unknown.

Take a few minutes to learn a little more about your system and how it works. When something does happen, you will have a little less stress armed with this knowledge.

Understand How Your System Works

An air conditioner is a beautifully simple system with two primary functions. First, it circulates air throughout your house. Second, it regulates the pressure of the refrigerant circulating through the system.

The refrigerant is what makes the air cold that comes out through your vents. The only way it does this is by changing pressure as it circulates. When pressure increases so does the temperature. Likewise, when the pressure decreases, the temperature drops.

The refrigerant absorbs the heat from the air inside then moves outside. As it does, the pressure is increased, intensifying the heat and allowing it to transfer to the air more easily.

Once it moves back into your house, the pressure is dropped quickly, resulting in substantially cold temperatures. This lower temperature allows for it to absorb a lot of heat from the air quickly.

The system must move warmer air from inside your house, through the area where the refrigerant absorbs its heat, then back out into your house.

What Do You Experience When Something Is Not Working?

When there is a major problem with the system, you are going to notice quickly. Many of the problems with your system may actually present similar symptoms. Combining these general symptoms with more specific ones associated with individual parts, allows you to identify the problem.

One of the first things you may notice when your system has a problem is the air coming from your system being warmer than normal. Along with this, you may notice there is less air volume coming from your vents.

If you do not notice these when they are still subtle, you will likely see your energy bills climbing. You may also notice extra moisture throughout your home. Now let’s look at the individual parts, what they do, and what may go wrong.

Circulating Fan

The circulating fan is also called the blower fan and is responsible for circulating the air through your system. It sits inside as part of your air handler or in our furnace.

As it spins, it will collect air contaminants that made it past the air filter. This will cause it to push out less air than normal, and may also cause it to spin off balance.

The fan motor is also prone to eventually burning out, especially if bearings are not lubricated regularly. When this happens, you may hear a rattling, screeching, or buzzing sound coming from your indoor unit.

Evaporator Coil

The evaporator coil is what actually makes your air cold when the A/C is running. The refrigerant passing through an expansion valve before entering the evaporator coil. This restricts the amount of refrigerant entering the coil, significantly reducing the pressure, and dropping the temperature.

The circulating fan then draws air through the coil, making the air cool before pushing it out into the house. As a result of all the air passing through the coil along with the condensation it forms, contaminants that were not caught by the filter will collect on it. Eventually, this will cause an airflow restriction if it is not cleaned regularly.

The major issue with evaporator coils is their relative fragility. Damage to the coil can cause a refrigerant leak in your home, which may be accompanied by a screaming sound. If you hear this, turn off your unit, and call for a repair technician.


Once the refrigerant absorbs the heat from the air inside the house, it moves to the condensing unit. The first thing that happens is it runs through the compressor, which forces it into a smaller space, increasing the pressure and temperature. This temperature increase allows it to transfer the heat more effectively to the air outside.

The fact this part is creating pressure makes it a little more prone to failing. As this fails, you may hear a clattering, growling, or screeching sound. If your compressor does fail, you will need to replace it. Your repair technician will help you determine if replacing the compressor alone is the best idea based on your air conditioner’s age and condition.

Condensing Coil

After the refrigerant goes through the compressor, it moves into the high-pressure condensing coil. Air from outside flows over the coil and absorbs the heat to be vented out.

Much like the inside coil, one of the biggest problems the condensing coil faces is being clogged with dirt, dust, and other contaminants. The best way to prevent this is to carefully clean it every season. However, if you are too rough, you can cause damage to the coil, and cause a leak.

Just like the inside coil, if you hear a screaming sound from the condensing unit outside you should turn off the system. In either case, running the system with low refrigerant can cause significant damage to the compressor.

Condensing Fan

Along with the condensing coil, the condensing unit also has a fan. This draws air in through the condensing coils, then vents it out of the top of the unit.

As this runs, the fan blades will eventually loosen, which may create a rattling or whirring sound. The fan motor may also burn out, causing a humming, screeching, or rattling sound.

During a regular maintenance visit, a repair technician will inspect your fan and fan motor. They will also tighten down your mounting screws or bolts.

Electrical Components

Aside from the major components of your system, there are also two primary electrical components. Both the contactor and capacitor are in the outside condensing unit.

The capacitor stores a large electrical charge to kick-start the compressor when it cycles on. When it fails, you will likely hear a loud buzzing or humming sound. You may also notice the compressor failing to initialize.

The contactor is also in the condensing unit and is the switch that controls the compressor. When the thermostat’s temperature reaches the threshold to turn on, it sends a signal, which activates the contactor. When it fails, it will either not activate, or will sound like chatter because it turns on and off regularly. This rapid cycling is very hard on the compressor and can cause damage.

Your system is designed to last 10-15 years when it is properly maintained, which should include most of these parts. Homeowners around Charlotte have trusted Integrity Heating & Cooling for over 35 years to keep their systems operating efficiently. Our team not only provides cooling and heating maintenance, repair, and installation, but also indoor air quality improvement and standby generator services. Call to schedule your seasonal maintenance visit with our team today.

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