Why Is My AC Not Working? 6 Common Causes Explained

Air conditioners are supposed to cool your home, not boil you to frustration. But just like any hardworking appliance, they can run into problems, often at the worst possible time. 

Fortunately, an AC not cooling is a usual problem expertly solved by reliable technicians. Most AC failures stem from a handful of common, fixable issues that expert HVAC technicians can repair and diagnose quickly.

Ready to learn what’s stopping your AC from keeping things cool? Let’s break them down! 

Dirty Air Filter

In usual cases of an AC not cooling, the simplest answer often lies in your filter. This seemingly innocuous piece of your HVAC equipment traps dust, dirt, pollen, and other airborne particles before they can enter your system and home. 

But many homeowners forget to clean or replace it. Over time, the trapped debris builds up and restricts airflow, making your AC system work overtime to keep up. In the worst case, it can even lead to a frozen evaporator coil—a more complex problem you’d want to avoid.

🛠️How to fix it: Check your air filter regularly (at least once every one to three months). Clean and replace it as needed. 

Learn more: DIY AC Repairs & Quick Fixes

Image Source: Shutterstock

Thermostat Issues

Another possible answer to the “Why my AC is not cooling” question lies in your thermostat, especially if you’re using smart models. If set incorrectly, malfunctioning, or has dead batteries, it could send the wrong signals to your AC system. This can result in your unit not turning on, short cycling, or blowing warm air. 

🛠️How to fix it: Check your mode and temperature settings, batteries, Wi-Fi connection, or software to see if they’re causing the problem. Your HVAC system’s manual should be a good reference if you’re unsure where to start! 

Dirt on Condenser Coils

The outdoor condenser unit of a central air conditioning system releases the heat that your indoor unit pulls from your home. Once the refrigerant absorbs heat from inside, it travels to the outdoor condenser coil, where that heat gets expelled into the outside air.

If you haven’t noticed, dirt does major damage to air conditioners. Since the condenser unit sits outdoors, it’s constantly exposed to dust, grass clippings, and debris. Over time, all that grime can coat the coils and cause an “AC not cooling house” issue behind your back. 

🛠️How to fix it: Check your outdoor unit now and then. If you see dirt or debris stuck to the fins, gently rinse the unit with a hose (never a pressure washer!)

Low Refrigerant Levels

If your problem is an AC running but not cooling, low refrigerant levels may be the culprit. AC refrigerants are chemical compounds that absorb warm indoor air from your home and release it outside. Without it, your AC unit is just a weird-shaped fan.

However, refrigerant doesn’t get “used up” like gas in a car. If levels are low, there’s likely a leak somewhere in your system, and you’re bound to see signs like:

• Warm air blowing from your vents
• Ice forming on the refrigerant lines or evaporator coil
• Hissing or bubbling noises from the unit
• High energy bills despite poor cooling performance

🛠️How to fix it: Unlike a clogged air filter, this AC not cooling issue can’t be DIYed. Call your trusted HVAC technicians ASAP if you see any of the signs above.

Image Source: Shutterstock

Frozen Evaporator Coils

Ironically, when your AC is too cold inside, it stops cooling your home. If you’ve done the preliminary “My AC is Not Cooling” checks above and still notice weak airflow or warm air coming from your vents, frozen evaporator coils could be the issue.

This piece of AC unit equipment contains the refrigerant responsible for cooling air. But when something disrupts airflow—like a clogged filter or blocked return vent—the coil can get too cold and freeze over. Once the coil is covered in ice, it can’t absorb heat properly, and your system stops cooling efficiently (or at all).

🛠️How to fix it: If you spot ice buildup or strange hissing or bubbling sounds, you might have frozen your AC. We suggest turning the unit off to prevent further damage while waiting for the pros to troubleshoot.

Faulty Capacitor or Motor

Another potential cause of the “AC not cooling” problem is a faulty capacitor or motor. These internal electrical components start up your AC and keep it running. When they malfunction, forget cooling—your AC may not even turn on. 

Some tell-tale signs of faulty capacitors and motors are:

• Humming noises or no sound at all when the unit starts
• Weak or no airflow from the vents
• AC turning on and off unexpectedly

🛠️How to fix it: Capacitor or motor problems can be difficult to diagnose if you’re not an HVAC professional. Since these parts carry an electrical current, it’s best to turn off your system and contact a technician immediately. They’ll know what to do!

AC Not Cooling? Leave It To The Experts at LG Home Comfort

An AC not cooling shouldn’t have to ruin your summer comfort. With LG Home Comfort, you get fast, reliable, and affordable solutions from a family-run business that truly understands what “home comfort” means.

We offer AC repair and maintenance services to quickly identify your problem, implement the right fix, and ensure it stays fixed for years to come. Our certified technicians are available 24/7 for emergency same-day service and next-day appointments, so you won’t have to endure another uncomfortable day in the heat. 

Don’t spend another day wondering, “Why is my AC not cooling?” Contact us today for a free in-home assessment and restore your cool comfort fast!