Why Is My AC Running but Not Cooling? (5 Common Causes)

There are few things more frustrating during a hot North Carolina July than hearing your air conditioner running, only to realize your home isn’t getting any cooler. You can feel the air coming from the vents, but it’s weak or warm, and the temperature inside just keeps climbing. It’s a common problem, and as your local comfort experts, we want to help you understand what might be happening.

Your job isn’t to diagnose a complex HVAC system—that’s what we’re here for. But understanding the potential causes can give you peace of mind and help you know when it’s time to call for professional help. Here are the five most common reasons your AC is running but not cooling.

Simple Fixes You Can Check Right Now

Before panicking, let’s rule out the two most frequent culprits. These are simple issues that you can safely check yourself in just a few minutes.

Cause #1: A Severely Clogged Air Filter

Your air conditioner needs to breathe. The air filter’s job is to trap dust, pollen, and other debris, but if it becomes completely clogged, it can choke off the airflow to your system. When this happens, the cold air your AC is producing can’t get into your home effectively. In severe cases, it can cause the evaporator coils to freeze over, completely blocking airflow.

• What to do: Locate your indoor air filter (often in a slot near your furnace or air handler) and check it. If it’s visibly grey, dirty, or clogged with debris, replace it with a new one. We recommend checking your filter monthly.

Cause #2: Incorrect Thermostat Settings

It may sound basic, but it happens more often than you’d think! A simple setting error can make it seem like your AC is broken. Before calling for service, it’s always worth taking a moment to double-check your thermostat.

• What to do: Ensure your thermostat is set to “COOL,” not “HEAT” or “FAN.” The “FAN” setting will circulate air continuously, even when the cooling cycle is off, which will feel like your AC isn’t working. Also, make sure the set temperature is lower than the current room temperature. If you suspect the device itself is the problem, learn more about the ways a malfunctioning thermostat can affect your AC.

Still not working? If you’ve checked the basics and your home is still hot, it’s time to call the pros. Schedule your expert diagnosis with Comfort Central now.

When It’s Time to Call a Professional: More Complex AC Issues

If you’ve checked the filter and thermostat and the problem persists, the issue is likely more complex and requires the tools and expertise of a trained technician. Attempting to fix these issues yourself can be unsafe and may cause more expensive damage.

Cause #3: Extremely Dirty Coils

Your air conditioner has two sets of coils: the evaporator coils inside and the condenser coils outside. The evaporator coils absorb heat from your indoor air, while the condenser coils release that heat outside. If either set is caked in dirt, grime, or yard debris, they can’t transfer heat effectively. With the high humidity we often experience in the Asheville area, wet leaves and grass clippings can stick to the outdoor coils like glue, making regular checks even more important. When the coils are dirty, your system will run and run, but it won’t be able to cool the air properly.

• What to do: This requires a professional cleaning. Our technicians use specialized tools and cleaners to safely restore your coils without damaging the delicate fins, ensuring your system runs efficiently again.

Cause #4: A Refrigerant Leak

Refrigerant (often known by the brand name Freon) is the vital substance that circulates through your AC system to cool your home. It is not a fuel; it doesn’t get “used up.” If your system is low on refrigerant, it means there is a leak somewhere. Signs of a leak include:

• A hissing sound coming from your AC unit.
• Ice or frost forming on the copper refrigerant lines.
• Your home taking much longer to cool than usual.
• What to do: A refrigerant leak is a serious issue that can harm both your system and the environment. Only a licensed professional is qualified to handle refrigerant. A Comfort Central technician will not just top off the refrigerant; we will locate and repair the leak to provide a lasting solution, which is central to our goal of building a trusted relationship with you.

Cause #5: A Failing Compressor

The compressor is the heart of your outdoor air conditioning unit. Its job is to pressurize the refrigerant and pump it through the coils. If the compressor fails, your AC system simply cannot cool your home. The fans may still spin and make noise, but the cooling cycle is broken.

• What to do: A compressor failure is a major repair that requires an expert diagnosis. A technician will need to test the unit’s electrical components to confirm the issue and recommend the best course of action, whether it’s a repair or a replacement.

Want to Avoid These Problems in the Future?

Regular maintenance is the single best way to prevent unexpected summer breakdowns. Most of the issues described here—like dirty coils and even refrigerant leaks—can be caught early during a professional tune-up. Our Comfort Club is designed to make this easy for you, providing seasonal maintenance visits, discounts on parts and labor, and priority service. It’s the surest way to enjoy worry-free comfort and keep your system running safely and efficiently.

Don’t Settle for a Warm House – Trust the Experts at Comfort Central

At Comfort Central, our goal is to provide the high-quality HVAC services you deserve. While a dirty filter is a quick fix, issues like refrigerant leaks and compressor failures require professional attention to protect your investment. All our repair work is backed by our 100% Satisfaction Guarantee, so you can call with complete confidence.

If your AC isn’t cooling, give us a call. We will diagnose the problem correctly and provide a clear, upfront solution to get your home cool and comfortable again.

Schedule professional AC repair in Asheville, Hendersonville, and the surrounding areas today. Call Comfort Central, Inc. at 828-483-4040 to restore your peace of mind!