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May 21, 2025

How Does a Central Air Conditioner Compressor Work?

A central air conditioner system is made up of three important parts: evaporator, condenser, and compressor.

In this article, No Problem Heating & Cooling is going to run you through how a central air conditioning compressor works, what you can do to maintain the system, and what kind of costs to expect if you need to replace the AC compressor.

What is an Air Conditioning Compressor?

 

While your AC compressor is located outside, it is really the heart of your AC system. Your compressor works the same way your heart does. The central air conditioning compressor is responsible for pressurizing and circulating the refrigerant, which enables the transfer of heat from inside your home to the outside environment, resulting in a cooler and more comfortable indoor temperature.

How Does Your Central Air Conditioner Work?

The compressor will pump refrigerant from your outside unit to the indoor unit. At this point, the refrigerant is cold, but it starts collecting heat and as it gets hot it turns into a vapor. At some point, it will not be able to grab any more heat and it travels back toward the compressor outside. Remember it is pulling that heat back with it. The refrigerant comes back to the outdoor unit as a superheated gas. Once the refrigerant loses this heat, it goes right back inside to start this process over again.

How to Keep your Central AC Compressor in Good Shape

Keeping your system in tip-top shape is going to help prevent most issues. No Problem Heating & Cooling offers a club membership that will keep your HVAC system protected all year long. Keeping your outdoor unit clean will be a big help. You will want to clean your system yearly outside. Pull your covers off and spray the dirt and bugs off on the condenser fins.

We see a lot of trees and shrubs that cover AC units that cause major problems with the system. Do not ever buy a decorative cover for your AC! If have trees, shrubs, or barriers that covers too much, it will suffocate your system.

What are the Signs of Low Refrigerant in My Central Air Conditioner?

Watch for low refrigerant. If your system is low on freon, the compressor will work harder to push enough refrigerant through the system to cool down your house. Possible signs could be:

  • The copper lines are warm
  • There is icing on your coils
  • Bubbling or hissing noise from your lines
  • Higher electric bills monthly
  • Warmer air instead of cooler air coming from your indoor vents
  • The AC will run constantly and not cool your home

It’s important to note that if your system uses an older type of refrigerant like R-22, you may need to upgrade to a more environmentally friendly refrigerant like R-410A. This can add several hundred dollars to the cost you may be expecting from past experiences.

How to Check for a Bad Compressor

If you are hands on and love the technical stuff, David Jones takes you through how to check for a bad compressor in this video:

For your safety and to maintain any available warranties, only a licensed HVAC technician should perform any work on your HVAC system.

How Much Does It Cost To Replace an AC Compressor?

The cost to replace a central air conditioning compressor can vary widely depending on several factors, including the size of your AC unit, the type of refrigerant it uses, your location, and the labor costs in your area. On average in the St Charles/St Louis area, you can expect to pay anywhere from $500 to $2,000 for the compressor replacement.

Can I Replace the AC Compressor or Do I Need a New One?

This is a tough question. AC compressor failure is fairly common when it comes to a whole system failure. Since the air conditioning compressor is crucial to the function of your AC system, generally the cost of replacement can get high. One of the biggest factors to determine if you should buy an entirely new air conditioning system is how old your current system is.  The HVAC technicians at No Problem Heating & Cooling will go over the specific pros and cons with you. Fortunately, there are many rebates and tax credits available for installing select high-efficiency units.

If you have questions about an air conditioner compressor, or if you need service for your air conditioner or need one installed, call No Problem Heating & Cooling!

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Ben Sanchez
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