If your AC is running but not cooling, you’re not alone. We get this question all the time, especially during the hotter months. The system sounds like it’s working, but the air feels warm or just not cold enough. That’s frustrating—and we know exactly how uncomfortable that can be. The good news is, there are some common culprits behind this issue, and many of them can be identified early. Let’s break it down.
Why Is Your AC Running but Not Cooling?
First things first—when your AC is running but not cooling, it usually means the system is trying, but something’s stopping it from doing its job. That “something” could be mechanical, electrical, or even user error.
Here are the most common reasons we see in the field:
Clogged or Dirty Air Filters Can Restrict Airflow
Yes, this one really is that important. A clogged air filter can reduce airflow dramatically, making your system work overtime for little payoff. When airflow is limited, your home won’t cool effectively—even though the AC is running.
Fix it:
Check your air filter. If it looks dirty or hasn’t been changed in over a month, swap it out. According to the U.S. Department of Energy, clean filters can lower your air conditioner’s energy consumption by 5% to 15%.
Your Thermostat May Be to Blame
Before calling in a technician, check your thermostat settings. Is it on the correct cooling mode? Is the temperature set lower than the room temperature? Sometimes, switching the fan setting from “On” to “Auto” also helps.
A malfunctioning thermostat could misread temperatures or fail to signal your AC properly. If the screen is blank or flickering, it may need new batteries or a reset.
Refrigerant Leaks: A Reason for AC Running but Not Cooling
If your AC is running but not cooling, a low refrigerant level or leak may be the cause. Refrigerant is responsible for absorbing heat from your home and releasing it outside. Without enough of it, your system can run continuously but still blow warm air.
You might notice:
Ice on the evaporator coil or refrigerant lines
Hissing or bubbling sounds
Longer cooling cycles with little temperature change
According to the EPA’s refrigerant leak repair requirements, leaks in systems with 50 pounds or more of refrigerant must be repaired if the annual leak rate exceeds 10%. Although most residential units fall below that threshold, all refrigerant handling still falls under EPA rules.
Only EPA-certified technicians are allowed to service AC systems using refrigerants like R-410A or R-454B. In fact, under the Clean Air Act Section 608, it’s illegal to knowingly release refrigerant into the atmosphere during service. Topping off a system without repairing the leak is also a violation.
If a leak is found, it must be properly fixed—not just recharged. Otherwise, your system will keep underperforming and you may face fines or loss of warranty coverage.
AC Running but Not Cooling? Your Condenser Might Be Dirty
The outdoor condenser coil plays a huge role in heat release. If it’s covered in dirt, grass clippings, or leaves, it can’t transfer heat efficiently. As a result, your system runs constantly without cooling your space.
Solution:
Turn off power to the unit and spray the coil gently with a hose to remove debris. However, for deep cleaning, it’s best to call in a pro to avoid damaging any components.
Frozen Coils and AC Running but Not Cooling
Frozen coils can block airflow and prevent cooling altogether. This usually happens due to low refrigerant, poor airflow, or dirty coils. You might notice:
Little to no air coming from vents
Ice buildup on copper lines or the indoor unit
If this happens, turn off your AC to let it thaw. Then schedule a service appointment to address the root cause. Frozen coils are one of the most common reasons we see an AC running but not cooling, and they can cause more serious damage if left untreated.
Want to understand the full list of causes and how to prevent this in the future?
👉 Read our in-depth guide on why your AC might be freezing up.
Duct Leaks Are a Hidden Energy Drain
Another reason your AC is running but not cooling could be leaky air ducts. According to ENERGY STAR, as much as 30% of cooled air can escape through unsealed or disconnected ductwork—especially in attics or crawl spaces.
That means your system works overtime, but the cold air never reaches your living space.
Electrical or Sensor Issues Can Interfere with Cooling
If internal sensors or circuit boards are faulty, your system may turn on but not function correctly. This is harder to detect without tools, but if you’ve ruled out the basics, it’s worth having a professional run diagnostics.
Also, look out for tripped breakers, especially if your system shut down briefly and started running again. Inconsistent power can prevent efficient cooling.
What to Do Before Calling a Technician
Before jumping to conclusions, try these basic troubleshooting steps:
Replace your air filter
Double-check your thermostat settings
Clear debris around the outdoor unit
Make sure all vents are open and unblocked
If none of those solve the issue, and your AC is running but not cooling, it’s time to call in the experts.
When to Call Rocket Air Heating & Cooling
At Rocket Air, we’ve seen every type of AC issue—from minor glitches to major component failures. We use advanced diagnostic tools, provide honest recommendations, and get the job done right the first time. Whether you need a refrigerant recharge, duct repair, or coil cleaning, we’ve got you covered.
We also offer seasonal maintenance plans that help prevent these problems before they start. Keeping your system clean and tuned up can boost efficiency and save you money in the long run.
Final Thoughts: Don’t Ignore the Warning Signs
If your AC is running but not cooling, it’s usually trying to tell you something’s wrong. Ignoring it can lead to higher energy bills, equipment damage, or full system failure. But with a little attention—and the right help—you can restore comfort quickly.
Wherever you live, don’t wait until a heatwave to take action. And if you’re in or around Modesto, CA, give Rocket Air Heating & Cooling a call today. We’re here to help you stay cool and comfortable, no matter what the season brings.
