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Here’s what you need to know about AC compressors

Most homeowners tend to think of their “air conditioner” as a single unit. However, your air conditioner is actually more of a collection of components that work together as a single system: from the wall-mounted thermostat that sends instructions to the unit and the blower in your attic to the outdoor condensing unit, refrigerant line, and the condenser. In this article, we’ll review one of the most critical of these components, AC compressors, including taking a look at how they work, what can go wrong with them, and when it makes sense to replace the compressor or the entire air conditioner.

For professional air conditioning repair here in Chicago and Northwest Indiana, give us a call. Our team is ready to help answer your burning cooling questions.

What are AC compressors?

All air conditioners (and heat pumps) operate on the same basic principle: they use refrigerant to transport heat energy from inside your home to the outside, repeating this cycle again and again until the air temperature in your home cools to what your thermostat is set to.

AC refrigerant is uniquely formulated for this purpose: when heated, it transforms from its liquid form into a gas. Upon releasing this heat energy, it goes back to being a cold liquid. Your air conditioner’s blower unit pushes air over this chilled refrigerant, which then absorbs more heat from inside your home.

To move in its closed loop, the refrigerant needs to be properly pressurized. That’s where the AC compressor comes into the picture. Just like a garage compressor you use to fill bike and car tires, AC compressors use energy (electricity) to generate the pressure needed to allow for refrigerant to move and change states. You might think of the compressor as a pump that keeps the entire cooling cycle moving. No compressor, no cooling.

What can go wrong?

Well, just like that compressor in your garage (or really any part of your air conditioner), the AC compressor can start to show signs of wearing down. While it’s built to handle some degree of heat—after all, it’s housed in the outdoor unit where heat energy is being actively dispersed into outdoor air—many premature compressor deaths are caused by overheating.


Unfortunately, the compressor is typically the first major component to go in an air conditioner as it ages. Most compressors last about 10-15 years, which roughly translates to the overall lifespan of most air conditioners. With the right preventative maintenance and some attention to the issues listed below, homeowners can typically extend the lifespan of their AC compressors to 15-20 years. However, just like everything, it’s only a matter of time before your compressor dies.


Overheating occurs when the heat energy released in the condenser (that’s the outdoor unit) cannot ventilate properly into outdoor air. Most often, this happens when nearby bushes, shrubs, trees, or decorations are too close to the AC unit. This causes hot air to become trapped in the unit, raising the temperature on the AC compressor until the component overheats and fails.

Refrigerant Leaks

Unlike your car which requires regular AC refrigerant “recharges” every few summers, the refrigerant in your air conditioner exists in a closed-loop system. In theory, you should never need to add more refrigerant. However, refrigerant leaks can occur and lead to low refrigerant. This puts stress on the compressor, which has to exert more effort to pump the remaining refrigerant enough to generate the cooling needed inside.

Low refrigerant issues and AC compressor issues are often interlinked, which is just another reason why it’s critical to call in a professional if you suspect your AC unit is losing refrigerant.

How much do AC compressors cost to replace?

The AC compressor is one of the most specialized and intricate parts of the air conditioner. As such, it’s a relatively expensive component to replace. Typically, the decision to replace a compressor comes down to the age of the system:

  • If the air conditioner is less than 10 years old, it and its compressor may be covered by the manufacturer’s warranty, provided the homeowner has continued to meet the eligibility requirements, such as scheduling annual maintenance.
  • If the air conditioner is more than 10 years old, most HVAC technicians may advise you just replace the entire system. In a rough analogy, putting a new compressor into an aging air conditioner is like replacing the engine in an old car—even with a new compressor, the other components are still aging.

What should I do if my air conditioner stops working?

The first thing you need to do is bring in a professional to take a closer look. There’s a number of things that can go wrong with an air conditioner, and sometimes issues aren’t always as cut-and-dry as they initially appear.

If you’ve already had a technician out from another company to take a look at the system, and they’ve recommended a compressor replacement, call us to have one of our NATE-certified technicians give you a second opinion. As mentioned above, AC compressor replacement is only typically the right way to go in a select number of circumstances. Otherwise, you’re potentially wasting money.