Replacing Just The Outside AC Unit: Sensible Or BIG Mistake?

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Air-conditioning systems are comprised of indoor and outdoor units. However, when one of these fails to function, the entire system is impacted. When the outdoor AC unit is to blame, many wonder whether replacing just the outdoor unit would be sensible or a huge mistake. 

Experts advise against replacing only the outdoor AC unit. Besides the risk of voiding your manufacturer’s warranty, there are many compatibility issues that can cause more problems. If your outdoor unit is no longer covered by the warranty, it is more sensible to replace the entire AC system. 

In this piece, we’ll break down everything you need to know about replacing only the outdoor AC unit. Firstly, we’ll explain the reasons this should be done. Once we’ve done this, we’ll look at the one exception to this and how you should proceed when your outdoor unit stops running. 

Is It Possible To Replace Just The Outdoor AC Unit?

An AC compressor unit
An outside AC unit

Your AC unit inside is working perfectly, but the outside unit is no longer running. Now you’re wondering whether it’s possible to replace just the outside unit. Of course, many consumers believe that this would be cheaper and would solve the issue with their AC. Unfortunately, that is not the case. 

Replacing only the outdoor AC unit could lead to even more troubles somewhere down the line. What may seem like an inexpensive solution at first could end up being even more costly. Due to this, it is not typically possible to replace only the outdoor AC unit. There are three main reasons for this! 

#1: There Are Compatibility Issues Between New & Old AC Units 

One of the main reasons you cannot replace just the outside AC unit comes down to the age of your HVAC system. Over time, the design of AC units has evolved. Due to this, many older AC units are not compatible with newer units. For instance, let’s briefly consider the refrigerant used by air-conditioning units. 

Many modern AC units have now switched to using a more environmentally-conscious refrigerant known as 410A. Older models, however, use a refrigerant known as R-22, which is an environmental hazard and is no longer produced or imported to the United States.  

These compatibility issues between newer and older units are why homeowners generally can’t replace only an outdoor unit. If your home is running an HVAC system that is more than ten years old, you won’t find an outdoor unit that is compatible with your AC system. 

#2: Mismatched HVAC Units Cause Havoc 

Above, we explained the different refrigerants that are used by older and newer air-conditioning units. Even if you were able to find an outdoor AC unit replacement that uses the same refrigerant as your indoor system, experts would still advise against replacing just the outdoor unit

There are numerous ways different air-conditioning systems differ. For one, the condenser coil of the outdoor replacement unit might not match the size of the evaporator coils within your indoor unit. You also run the risk of having outdoor and indoor units with different manufacturers or SEER ratings. 

These factors can lead to many issues down the line. Your energy bills are likely to be higher when replacing only an outdoor AC unit. That’s because your energy efficiency will be reduced. Furthermore, you risk exasperating the wear and tear of your AC units, both indoor and outdoor, which can lead to the premature failure of your HVAC system

#3: You Risk Voiding Your AC Unit’s Manufacturer Warranty 

When your air-conditioning system was first installed, you would have received a warranty from the relevant manufacturer. Of course, this warranty covers you in the event of a component failure due to a manufacturing error. However, these warranties have an important stipulation many consumers are not aware of. 

For your air-conditioning system’s warranty to remain valid, the indoor and outdoor units must be matched. This means that replacing only one of these units, such as a malfunctioning outdoor AC unit – would void an active manufacturer warranty. However, if you’re still covered by this warranty, there may be another solution for you! 

When Can You Replace Just The Outside AC Unit? 

In the previous section, we considered the reasons AC experts do not recommend replacing only the outdoor AC unit. The reasons for this mainly come down to compatibility between different units, in terms of:

  • Age
  • The refrigerant used
  • Coil size
  • SEER rating
  • Manufacturer

Another reason was that, by replacing only one of the system’s units, you effectively void your AC system’s manufacturer warranty. However, if your air-conditioning system is still covered under a manufacturer’s warranty, there may be an easy solution to your problems! 

Generally, if your AC system is not older than five years, you will still be covered by this above-mentioned warranty. If this is the case, you might be able to get an outdoor unit replacement as part of your manufacturer’s warranty. There are three steps to this process! 

Step One: Check Your Manufacturer’s Warranty Status 

The first step, of course, is to check the status of your AC system’s warranty. To do this, you’ll need to go to your outdoor AC unit. There, you’ll want to locate a metal panel, which is generally situated on the side of the unit. This panel will contain your AC unit’s model number:

By going to the website of your system’s manufacturer, you’ll be able to search the model number of your system. This will allow you to determine whether your air-conditioning system is still covered by this warranty. If it is, you can proceed to the following step! 

Step Two: Consult Your Manufacturer’s Warranty 

If your HVAC system is still covered under warranty, the next step is to consult the warranty’s terms and conditions. When your system was initially installed, you may have received a copy of this. If not, you’ll be able to locate these terms and conditions on the manufacturer’s website (such as this one from Hannabery, which is found by Googling “Hannabery HVAC warranty T&Cs”)

Once you’ve located this document, you’ll need to check what is stated about your outdoor unit. If your exterior air-conditioning unit is covered in this warranty, there’s a good chance you’ll be able to get your outdoor unit replaced without needing to replace the entire AC system. 

Step Three: Contact The Manufacturer 

If your AC system is still under a warranty that covers the outdoor unit, it’s time to contact your air-conditioner’s manufacturer. They will be able to guide you through the claims process. When this is done, a replacement for the outdoor unit will be sent to you. 

Of course, this unit will be perfectly compatible with your indoor system. In this way, you avoid the reasons we discussed in the first section regarding the risks of replacing just the outdoor system, making this the one exception to the rule! 

What To Do When Your Outside AC Unit Isn’t Working?

A contractor repairing an AC unit
A contractor repairing part of an AC unit

Thus far, we’ve established that experts do not recommend replacing just the outside air-conditioning unit. Now, you might be wondering about how to proceed with your malfunctioning outdoor unit. Of course, the first step would be to check if this is still covered by the manufacturer’s warranty, which we discussed above. 

However, if your warranty has expired, it likely means your AC system is older than 5 years. According to the Department of Energy in the United States, HVAC systems should be replaced every ten to fifteen years. If your AC system is older than ten years and your outdoor unit has failed, the most sensible solution would be to replace the entire system

However, if your system is not that old, you can hire a professional to assess your outdoor unit. There are numerous reasons why your outdoor AC unit might be malfunctioning. An expert would be able to troubleshoot this and may be able to repair your system. Of course, this would fix the issues you’ve been experiencing with your HVAC system. 


When your outdoor AC unit stops working, you might be tempted to just replace the outside unit. However, due to compatibility issues, this is not advised by experts. You should first consult your manufacturer’s warranty and attempt to repair the outdoor unit. If you need to replace the outdoor unit, it’s advised you replace the whole system to avoid any issues.

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About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.