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Why is my AC running but not cooling?

May 19, 2020

A homeowner attempting to turn on her AC unit by clicking the button on the white AC remote.

As summer approaches, an AC unit that runs but fails to cool is exactly what you don’t want. If you find that your home’s air conditioner is not cooling your house but rather blowing warm air through your vents (or even hot air), you don’t necessarily need to prepare yourself for the worst. 

While serious AC issues will require a professional air conditioning repair technician to resolve them, there are some AC fixes you can do yourself. Here is a brief list of reasons why your air conditioner is not working.

Reasons Why My AC is Running But Not Cooling

1. Incorrect Thermostat Settings

This is a quick, easy fix that could be a solution to your AC issue. Double check your thermostat to see what setting your AC fan is on. If it’s set to “ON,” then that means your AC fan will blow constantly, regardless of when the air is being cooled. If you’ve noticed that your AC is blowing air through your vents all day but sometimes it’s lukewarm, this could solve your issue.

Go to your thermostat and switch the fan setting to “AUTO” so it no longer blows constantly, but rather only blows when the AC unit is cooling your home’s air.

2. Old Air Filter

A clogged air filter is one of the easiest ways to break your AC unit or make it ineffective. If you’ve checked your thermostat and all the settings are to your liking but your unit is still blowing warm air, try checking your air filter. If it’s obviously dirty, replace it.

A dirty air filter forces your AC unit to struggle with air circulation, meaning your home won’t remain at the temperature you've set. It also puts stress on the evaporator coils, which are responsible for physically cooling your home’s air. Extra stress due to a clogged air filter can cause these coils to freeze, turning them into a block of ice that blocks air flow. 

If your air conditioner is not running or if you want to ensure your air filter never causes issues for your AC unit, be sure to replace it regularly. The exact regularity that you should install a new air filter depends on your indoor air quality, household size, the number of pets in your home, the air filter model, the air pollution levels around your home, and if anyone living in the home has allergies or illnesses. 

For a typical suburban home, you should change your air filter anywhere from every 30 to 90 days. 

3. Dirty Compressor

Part of your regular AC maintenance check-ups should include cleaning in and around your compressor. As seasons go by, dirt, leaves, and other debris collect, preventing your AC unit from running as it should.

While some homeowners tackle the task of cleaning their compressor themselves, most see the best results when bringing in a professional HVAC technician to handle the job. This will not only ensure that the unit receives a deep and thorough clean, but it will also mean avoiding damage and injuries caused by lack of experience.

4. Low Refrigerant Levels

Not only do low refrigerant levels prevent your AC from properly cooling your home’s air, but they may also indicate that there is a refrigerant leak in need of repair. 

Checking the refrigerant levels of your unit should always be done by a professional since the measurements must be exact. Too much or too little and your unit will be negatively impacted—not to mention the refrigerant chemicals can be dangerous if mishandled. 

5. Power Issues

If you’re wondering, "Why is my AC running but not cooling?" but you’ve ruled out all the issues listed above, then you could have a power-related issue. This might be as simple as making sure the unit is plugged into a power source and its power cord is still intact, but it could be a more complicated, internal issue.

Is your AC unit making noises? Does the air it’s blowing have an odor? Has performance been slowly affected for weeks or are you experiencing issues all of a sudden? These are all important questions to ask to identify the real issue. The fan or motor could be struggling, there could be a tripped circuit breaker, or there could be some other severe problem with your electrical panel. 

Don’t attempt to handle AC power issues on your own—always call in a professional for that type of work to protect your unit from additional damages.

Want to Get Ahead of the Issue?

Get ahead of cooling problems before the heat sets in. The last thing you want to deal with is sitting in a warm house while you wait for a technician’s busy summer schedule to open up. CroppMetcalfe offers air conditioning service and repairs across the DMV at manageable costs to homeowners.

If your air conditioner isn’t performing adequately, call our 5-Star Technicians at 703-698-8855 or schedule an HVAC appointment online today.


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"I've been a CroppMetcalfe customer for 9 years and you have always provided outstanding service. I just had my semi-annual maintenance done, and I wanted to thank George for the truly outstanding service, professionalism, and excellent advice. He is definitely one of the best 5-Star Technicians I've had! Thank you CroppMetcalfe!"

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