What Are the Major Parts of an Air Conditioner?

April 12, 2021
Central Air Conditioning in Seattle, Washington

It can be difficult feeling like you don’t know what is going on when talking with air conditioning technicians. Yup, you know there are parts of the system, and you know you are having a problem. But do you know the difference between the condensing coil and the evaporator coil, or what the compressor actually does?

This lack of understanding often leads to stress and questioning whether a technician is being honest. To combat this, take a few minutes to learn about your system, the signs of a problem, and the major components.

Your System: An Overview

At a high level, your system circulates air and circulates refrigerant. The refrigerant absorbs heat from the air inside and transfers it to the air outside. To do this properly, the system has to constantly circulate warmer air from inside your home through the system.

For the refrigerant to do its job, the pressure has to be regulated throughout the system. As the pressure increases, the heat absorbed is intensified, allowing it to be more easily transferred to the air outside. When it decreases, it then becomes frigidly cold, allowing it to once again absorb more heat.

If there is a problem with the pressure regulation or the flow of air, your system will experience problems. Regardless of the kind of problem your system is having, you will probably experience some common problems.

How You Know You Have a Problem

If you have had a subtle problem for a while and have not noticed it yet, you may notice increased energy bills. However, if you get to the point of noticing this over several months, you may have caused additional damage to your system.

Before your energy bills start creeping, you will probably notice your system is putting out warmer air than it should while running. You may also notice the amount of air coming from your vents is not as much as normal.

Or, maybe the humidity in your air is higher than normal. This is a tell-tale sign the system is not cooling the refrigerant properly. Avoid assuming it is just because of an increase in humidity in the outdoor air.

Beyond these general symptoms, you may notice specific symptoms for the component where the problem resides. The following are the major components, and what you may notice about each.

Circulating Fan

The circulating fan is in your indoor unit and is the fan responsible for drawing air into your system. It then forces it through the evaporator coil and back out into your house.

Being the fan runs for both your air conditioning and heating, it tends to collect contaminants that make it past your air filters. As such, it is important to clean it during regular system maintenance to prevent lower airflow through the system.

These fans can also get off balance, causing additional strain on the motor. The motor also has bearings that need to be lubricated if it is not a sealed system.

If your circulating fan has a problem, you may notice some odd sounds coming from the inside system. This may be a rattling, a squealing, or even a buzzing sound.

Evaporator Coil

Your evaporator coil sits inside, usually as part of your furnace unit or near your air handler. As the refrigerant enters the coil, it passes through an expansion valve, which reduces the pressure. This is what makes the evaporator coil so cold, and allows the refrigerant to absorb so much heat from the air passing over it.

Like the circulating fan, the coil tends to collect contaminants, restricting the flow of air through the coil. To reduce this risk, you need to have the evaporator coil cleaned during regular maintenance.

The most common problem you may experience with an evaporator coil is a refrigerant leak. This may be accompanied by a hissing or screaming sound. If you suspect a refrigerant leak, turn your system off immediately and call for a repair technician.

Running your system with low refrigerant can cause significant damage to your compressor. If the leak is inside, it also poses a danger to your house’s inhabitants.


The compressor is what increases the pressure of the refrigerant as it arrives at the outside condensing unit. This allows the heat absorbed from inside the house to more effectively transfer to outside the house.

If your compressor stops working properly, the air will not be as cold as it should be. You will also likely hear some noise coming from the outside condensing unit. The sounds you are likely to hear include screeching, rattling, or even growling.

You may also notice your circuit breaker tripping when the system is cycling on. If your compressor is failing, a technician will have to evacuate the refrigerant to replace the component. A such, it makes the report very expensive.

Your technician will help you evaluate the cost of this kind of repair, along with the overall age and condition of your system. It may be more advantageous to replace your condensing unit to reduce long-term repair costs.

Condensing Coil & Fan

The condensing coil is what contains the high-pressure refrigerant, and allows it to transfer heat to the outside air. In order to transfer the air, it must have air flowing through the coils. The condensing fan draws that air through the coils and then vents it out the top of the unit.

If the condensing coil has a problem, it will likely be a refrigerant leak. Just like inside, this may have a hissing or screaming sound with it, depending on the severity.

You are more likely to run into problems with the condensing fan. You may hear a rattling or whirring sound if the fan blades loosen. If the fan motor is going bad, you may hear a humming, buzzing, rattling, or screeching sound.

If your fan motor goes bad, this is a relatively simple replacement and does not interfere with the refrigerant system. However, if the coils are bad, then you again are looking at a substantial repair.

The best way to keep your condensing coil and fan working properly is through regular maintenance. During a maintenance visit, a technician will wash the outside of the condensing unit, allowing air to flow. They will also check and tighten the fan blades, and the mounting screws or bolts to prevent unnecessary vibration.

Knowing when your system is having problems is a significant step in keeping it working well. Attending to possible problems early will not only keep the cool air flowing but reduce your repair bills.

Brennan Heating & Air Conditioning has been the trusted choice for air conditioning repair and maintenance around Seattle for over 30 years. People have also relied on us for heating installation, repair, and maintenance, as well as full water heater and electrical services. Call to schedule your air conditioning repair with one of our technicians today.

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