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What to Do if Your Air Conditioner Is Not Cooling

Written by Joe Roberts

Published on June 2, 2023


What to Do if Your Air Conditioner Is Not Cooling

If your AC system isn’t blowing cool air, even when the unit is running, check our guide. We’ll help you troubleshoot and solve common AC problems.

To provide you with the most accurate and up-to-date information, we consult a number of sources when producing each article, including licensed contractors and industry experts.

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Is your air conditioning unit dropping the ball this summer? If you just can’t bring your home to your desired temperature no matter how long you keep your air conditioner running, it might be time for a tune-up. Hiring a professional HVAC technician is the best way to make your system provide cold airflow again, but sometimes, you can fix your AC yourself!

In fact, some of the most common reasons air conditioners malfunction are well within the average homeowner’s ability to fix. Keep reading, and we’ll teach you how to change dirty air filters, clear out clogs around your condenser unit, and solve other common problems.

Leave the AC repair to an HVAC technician

Check your thermostat

You’ve likely already done this, but it never hurts to double and triple-check that your thermostat settings are correct, especially if you don’t live alone. Someone else may have messed with the thermostat since you last looked at it. Check that the thermostat is set to “Cool” instead of “Heat” or “Fan,” and make sure that the temperature is where you want it.

After taking these steps, give the system a few minutes, then put your hand over one of your vents to feel the air. If it isn’t noticeably cooler than room temperature, you have a more serious problem than the thermostat. 

Inspect your air filter

Your AC system’s air filter(s) needs to be replaced every few months. As your system runs, its filter fills with dust, pet hair, and other airborne debris. After extended periods of heavy usage, this buildup can significantly decrease airflow to your central air conditioner and make your fan motor work overtime. Since your system can’t intake and purify air as efficiently with a dirty filter, excessive buildup can also lower the air quality in your home.

Your system’s filter may be located near your indoor air handler, but it could also be inside an intake vent in one of your walls or ceilings. Some systems even have multiple intake vents, each with its own filters.

To determine where your filter is located, first check for a slot where your air ducts meet your furnace. If your system filters air near your air handler, this is where the filter will be. If you don’t find an air filter slot in that location, it’s likely positioned over an intake vent.  

Intake vents – also called return vents – are usually much larger than supply vents, so finding out which vents might have filters is easy. Run your system for a few minutes and put your hand over all of your home’s largest vents. If you feel air moving into instead of out of a vent, that’s an intake vent. Open it up to find the air filter.

If you find a filter clogged with debris, replace it immediately. Go to the hardware store, pick up a new filter of the same size, and install it in the same place where you removed the old one. Be sure to orient the filter in the correct direction inside its slot or vent. There should be arrows on the sides of the filter indicating airflow direction.

Once you’ve installed your new air filters, run the system again. If it doesn’t start blowing cool air within a few minutes, the air filters weren’t the cause of your air conditioning woes. 

Make sure none of your ductwork is leaky

When you run a central HVAC system, a blower pumps cold or warm air throughout your home through air ducts, so the circulation of the entire system depends on airtight ductwork. Unfortunately, though, ducts can come loose and crack over time. When this happens, it causes a system to leak conditioned air, meaning the air won’t reach all of the home’s rooms.

This problem can be hard to diagnose properly. Some of your system’s ducts may be built into walls and ceilings, so you can’t fully inspect them without cracking the drywall open. If you suspect covered ducts might be leaking, you’ll need to call in professionals. However, you can easily inspect any exposed ductwork yourself. While your system is running, go over every inch of unenclosed ductwork in your house and look for air leaks. 

If you find any leaks, you can try to tighten or even replace the leaky segments yourself if you’re handy. If you’re not sure you’re up to the task, you can cover the leaks with duct tape. This won’t look as good as replacing broken segments, and it may not last very long, but it should get the cold air flowing again.

If you don’t find any air leaks, or you fix them, and it doesn’t restore cold airflow to your entire home, move on to the next recommendation. 

Remove debris from the condenser unit

Most central AC systems have an outdoor condenser unit that does a lot of the most important work in the air cooling process. Your condenser is most likely in your backyard, on the side of your house, or on your roof. Condenser units usually look like large boxes with grating around the outside, and they typically include three components:

  • A compressor that circulates an HVAC system’s refrigerant from the home to the condenser
  • A condenser coil (or several) for hot refrigerant to run through and disperse heat
  • A condenser fan that blows hot air out of the unit, allowing the refrigerant to cool before returning to the home

Because condenser units are typically placed outside a building, they are vulnerable to falling leaves, airborne dust, branches, and other debris. If a unit’s exterior gets blocked up by this debris, it can prevent the fan from properly doing its job of cooling the refrigerant in condenser coils.

Luckily, this issue can be pretty easy to diagnose and solve. Simply inspect the exterior of your condensing unit for buildup and remove any debris you find. For safety, be sure to turn your system off before attempting this.

If your condenser’s exterior isn’t clogged or removing any debris you find doesn’t restore cold airflow to your home, it’s time to call in the big guns. 

Hire professionals to repair your AC unit for you

HVAC appliances are highly complex, and they include many moving parts, so many things can go wrong in any system. If none of the fixes we’ve listed get your cold air going again, the issue could be caused by any number of serious underlying problems like refrigerant leaks, frozen evaporator coils, a faulty condenser, or a broken fan.

These problems require specialized training to rectify, so you’ll need to hire a professional HVAC technician. This will likely cost you a couple hundred dollars on the low end, but it beats toughing it out in the summer heat. Luckily, if your system is under warranty, you may be able to get your installer or manufacturer to cover some of the costs.

It’s also worth mentioning that your AC system may be working perfectly. It’s just incorrectly sized for your home and can’t keep up with your cooling needs. This might mean you need to completely replace your air conditioner, a job that can cost thousands of dollars. 

Troubleshooting your AC

Air conditioners are more than just modern luxuries. In some regions and climates, they’re an essential safety measure and part of everyday life. So if your AC unit begins to fail, its impact is immediately noticeable, if not downright distressing. But with the quick fixes we’ve outlined, you’ll likely be able to get your AC up and running again. If all else fails, we recommend contacting an HVAC repair company right away. 

Hire an HVAC professional to do the job right

Written by

Joe Roberts Content Specialist

Joe is a home improvement expert and content specialist for Fixr.com. He’s been writing home services content for over eight years, leveraging his research and composition skills to produce consumer-minded articles that demystify everything from moving to remodeling. His work has been sourced by various news sources and business journals, including Nasdaq.com and USA Today. When he isn’t writing about home improvement or climate issues, Joe can be found in bookstores and record shops.