Why Your AC Is Running But Not Cooling

It’s one of the most frustrating things that can happen on a hot summer day in West Michigan: your air conditioner is running, but your home just isn’t cooling down. You can hear the hum of the system and feel air coming through the vents—but it’s not cold. If this sounds familiar, you’re not alone. At Third Coast Heating and Air, we hear from homeowners every summer with this exact concern.

The good news? While this issue is inconvenient, it’s often the result of common, fixable problems. In this post, we’ll walk you through the most likely reasons why your air conditioner might be running but not cooling your home—and what you can do about it.

A Dirty Air Filter Could Be to Blame

Let’s start with one of the simplest and most common culprits: a dirty air filter. Your HVAC system depends on proper airflow to function efficiently. When your air filter becomes clogged with dust, pet hair, pollen, and other debris, that airflow is restricted. As a result, your system can run continuously without ever delivering enough cool air to your living spaces.

Not only does a clogged filter reduce cooling effectiveness, but it also puts unnecessary strain on your AC system—leading to higher energy bills and potential long-term damage. We recommend checking your air filter every month during the summer and replacing it at least every 60 to 90 days. If you have pets or live in a dust-prone area, you may need to replace it more frequently.

Thermostat Settings Matter More Than You Think

Before calling for service, it’s always a good idea to double-check your thermostat. It may sound obvious, but many homeowners don’t realize their thermostat is set to “fan” instead of “cool.” When in “fan” mode, your system will blow air through the vents, but it won’t be actively cooling it. This can create the illusion that your AC is running but not working.

Make sure your thermostat is set to “cool,” and that the target temperature is lower than your current room temperature. If your thermostat isn’t responding, the batteries might need to be replaced. For older or programmable thermostats, double-check your settings to ensure a schedule or programming issue isn’t getting in the way of comfort.

Frozen Evaporator Coils Can Stop Your AC in Its Tracks

Another common reason your AC might be running without cooling is frozen evaporator coils. These coils are located in your indoor unit and are responsible for absorbing heat from your home. When airflow is restricted—often due to a dirty filter or low refrigerant levels—the coils can get too cold and develop a layer of ice. This ice prevents them from doing their job, which means your system runs and runs but never cools your space.

If you suspect frozen coils, turn off your AC system and switch the fan to “on” to help circulate air and thaw the ice. You’ll likely need to give it several hours. Once it’s thawed, the system may return to normal—unless the underlying issue isn’t addressed. In that case, it’s time to schedule a professional inspection to prevent the problem from returning.

Low Refrigerant or a Refrigerant Leak Could Be the Issue

Your AC system relies on refrigerant to cool your home. When refrigerant levels are low—often due to a leak—your system can’t effectively remove heat from your indoor air. You might hear a hissing noise or see frost forming on the refrigerant lines. In many cases, your system will run longer and longer while providing less and less cooling.

This is not something you can fix on your own. Refrigerant handling requires EPA certification and must be done by a licensed HVAC technician. If you suspect low refrigerant is behind your cooling issues, contact Third Coast Heating and Air to schedule a system diagnostic and recharge.

A Dirty Outdoor Unit May Be Blocking Heat Release

The condenser unit outside your home plays a critical role in the cooling process. It releases the heat absorbed from inside your home into the outdoor air. If the unit is covered in dirt, grass clippings, or other debris, it can’t release that heat effectively. As a result, the system becomes less efficient—and your home stays warm.

We recommend visually inspecting your outdoor unit and gently rinsing off any visible debris using a garden hose. Be sure to shut off power to the unit first for safety. Avoid using a pressure washer, as it can damage the delicate fins on the coil. For a more thorough cleaning, our technicians can provide a professional service during a tune-up visit.

Your System May Be Aging or Improperly Sized

Sometimes the issue isn’t something that can be fixed—it’s a matter of your system reaching the end of its lifespan or being the wrong size for your home. Air conditioners typically last 10–15 years, and as they age, their efficiency drops significantly. A system that once kept your home cool may now struggle to keep up, especially during heatwaves.

Improper sizing is another issue we see. If your AC unit is too small for your square footage, it may run constantly without ever achieving the desired indoor temperature. On the flip side, an oversized unit may short-cycle, turning on and off frequently without properly dehumidifying the air—leading to discomfort and higher humidity levels indoors.

If you’ve had ongoing issues with cooling or know your unit is older, it may be time to consider a replacement. At Third Coast Heating and Air, we offer free in-home estimates to assess your system and recommend options tailored to your home and budget.

Call the Experts at Third Coast Heating and Air

If your air conditioner is running but not cooling, don’t wait for the problem to get worse. What might start as a simple fix can quickly turn into an expensive repair—or a complete system failure—if ignored.

At Third Coast Heating and Air, we’re proud to serve homeowners across Holland, Zeeland, Saugatuck, Fennville, West Olive, and surrounding communities with fast, reliable, and honest HVAC service. Whether it’s a tune-up, repair, or system replacement, we’re here to help you stay comfortable all summer long.

📞 Call us today at (616) 209-8019
🌐 Or schedule your service at www.thirdcoastheating.com

Bonus: Prevent Future Problems with a Summer AC Tune-Up

One of the best ways to avoid cooling issues altogether is with routine maintenance. Our summer ac tune-ups include a thorough inspection, coil cleaning, refrigerant check, and more to ensure your system is ready for the heat. Ask us how you can join our maintenance program for year-round peace of mind.