Why Is My AC Running But Not Cooling?

It’s a hot summer day in Connecticut, and your air conditioner is humming along—but the house still feels uncomfortably warm. You check the thermostat. It’s set to cool and the fan is running, but there’s no relief.


If your AC is running but not cooling, don’t panic—there are a few common causes behind this frustrating issue, some of which you may be able to troubleshoot without a call for AC repair services.


At Town Oil, we’ve been helping local homeowners stay comfortable since 1963. We understand how stressful HVAC issues can be, especially when you're unsure whether it’s a simple fix or a more involved repair. Our goal is to help you make informed, pressure-free decisions and get your home back to a cool, comfortable temperature as quickly and affordably as possible.


Let’s take a look at the most common reasons your AC might be running but not cooling, what you can troubleshoot, and how our experienced air conditioning repair technicians fix each one.


Dirty Air Filter

A clogged air filter is one of the most common (and easily overlooked) reasons an air conditioning system runs without cooling properly. When the filter gets dirty, it blocks airflow, making it harder for your system to do its job. This can lead to warm air blowing through your vents—or even cause the system to freeze up.


Good news—this is something most homeowners can handle on their own. Locate your air filter (usually in the return vent or inside the indoor unit), slide it out, and check if it looks dusty or clogged. If it’s been more than a few months—or if you can’t see light through it—it’s time for a replacement. Just make sure to use the correct size and type for your system.


If you’ve replaced the filter and your central air conditioning system is still running without cooling, give us a call for AC service. There may be a deeper issue affecting your system’s airflow or performance. Our air conditioning repair team will diagnose the problem and get things running smoothly again—with clear communication every step of the way.


Thermostat Issues

If your air conditioning unit is running but not cooling, the issue might not be the system itself—it could be the thermostat. A faulty or miscalibrated thermostat may not be sending the right signals to your cooling system. Sometimes, it’s set incorrectly, the batteries are dead, or it's installed in a spot that throws off its temperature readings (like near a window, vent, or heat source).


Before calling for service, try a few simple troubleshooting steps:


  • Check the Settings: Make sure the thermostat is set to cool and the temperature is set lower than the current room temperature.
  • Replace the Batteries: If your thermostat uses batteries, low power can cause it to malfunction. Swapping in fresh batteries is a quick fix that often solves the problem.
  • Inspect the Display: If the screen is blank or flashing, that’s a sign the thermostat isn’t communicating properly with your AC system.
  • Give It Time: After changing settings or replacing batteries, wait a few minutes—some systems take a moment to respond.


If the thermostat seems unresponsive or your air conditioning system still isn’t cooling, it could be miscalibrated or failing internally. Our technicians can test the thermostat, recalibrate it if needed, or recommend a modern, energy-saving replacement. We’ll walk you through your options clearly—no upselling, just honest advice.


Refrigerant Leaks or Low Refrigerant Levels

Your cooling system needs refrigerant to absorb heat and cool the air. If there’s a leak or your system is low on refrigerant, it may run continuously without effectively cooling your home.


This isn’t a DIY issue—qualified HVAC companies are the only ones who can handle refrigerant. Our EPA-certified HVAC technicians will inspect your system for leaks, repair any damaged lines, and recharge the system to manufacturer specifications. We’ll also explain whether an air conditioning repair or full replacement makes the most long-term sense based on the age and condition of your unit.


Frozen Evaporator Coils

Evaporator coils are located inside your indoor unit. They absorb heat from the air, but if something restricts airflow—like a dirty filter, blocked vent, or low refrigerant—the coils can freeze up. When that happens, your system might blow warm air, run constantly, or stop cooling altogether.



If you feel comfortable, you can remove the front panel of your indoor unit and carefully look for ice or frost around the coils or tubing. If the coils are frozen, try these troubleshooting steps:


  • Turn Off the System: Let the coils thaw naturally by switching your thermostat to Off and just running the Fan setting. This helps circulate air and speeds up the defrost process.
  • Check Your Air Filter: A clogged filter can cause airflow issues that lead to freezing. Replace it if it’s dirty.
  • Make Sure Vents Are Open and Unblocked: Closed or obstructed vents can also limit airflow and contribute to coil freeze-ups.


If ice keeps forming after thawing or your AC still isn’t cooling properly, it’s time to call in the pros. Persistent freezing often points to deeper issues like low refrigerant, a faulty blower fan or motor, dirty coils, or airflow restrictions inside the ductwork. Our HVAC contractors will pinpoint the cause, perform any necessary AC repair services, and explain what happened.


Condenser Unit Problems (Outdoor Unit)

Your outdoor condenser unit is responsible for releasing the heat pulled from inside your home. If it’s dirty, blocked by leaves or debris, or has a mechanical issue—like a failing fan motor or capacitor—your system may run but struggle to cool effectively.


Over time, grass clippings, leaves, dirt, and even overgrown shrubs can block airflow around your outdoor unit. Here’s what you can safely do to troubleshoot:


  • Turn off power to the unit at the disconnect box or breaker before doing any cleaning.
  • Clear away leaves, twigs, and grass from around the base of the unit.
  • Trim back any plants or shrubs to leave at least 2 feet of space on all sides.
  • Gently rinse the fins with a garden hose (on a low setting) from the outside in—never use high pressure, and don’t bend the metal fins.


If your unit is clean but your AC still isn’t cooling, it may be due to a failed condenser fan, electrical issues (like a bad capacitor or contactor), dirty or damaged condenser coils, or refrigerant problems.

Our air conditioning repair team will run a full diagnostic and get your system back in shape quickly. We’ll explain everything clearly, walk you through your options, and never pressure you into a service you don’t need.


Electrical or Capacitor Issues

Your air conditioner relies on a number of electrical components to start and run properly. If a capacitor is failing or a circuit isn’t functioning correctly, the unit may power on but not actually cool.


Our trained HVAC technicians will run a full system diagnostic to test for electrical issues. If a capacitor, relay, or fuse is to blame, we’ll replace it quickly and safely. We always prioritize transparent pricing and timely service to get your system back up and running with minimal disruption.


Aging or Undersized Cooling System

Sometimes, the issue isn’t with a specific component—it’s the cooling system itself. If your air conditioning system is more than 10–15 years old or was improperly sized for your home, it may struggle to keep up, especially during peak summer temperatures.


If your system is nearing the end of its lifespan, we’ll walk you through your replacement options without any sales pressure. Town Oil performs HVAC installation for high-quality, energy-efficient systems from trusted brands like Heil, American Standard, and Fujitsu (for mini splits). We’ll explain the benefits of each and help you choose an air conditioning solution that fits your budget and your home’s unique needs.


How Town Oil Makes the AC Repair Process Stress-Free

We understand that when your air conditioning system stops cooling, you want fast answers and honest solutions—not scare tactics or upsells. That’s why our team approaches every air conditioning repair with clarity and respect:


  • Prompt Service: We respond quickly, especially in peak season, to diagnose and resolve issues fast.
  • Clear Explanations: We’ll walk you through the problem and your options in plain language—no jargon.
  • No Pressure: We provide honest recommendations and let you decide what’s best for your home and budget.
  • Quality Service Technicians: Our team is experienced, courteous, and trained to work with a wide range of cooling and heating system equipment, including heat pumps and ductless systems.
  • Trusted Since 1963: With three generations of family ownership and deep roots in the community, we treat our customers like neighbors—because they are.
  • Maintenance Solutions: After fixing the problem, we’ll share how regular maintenance services can help prevent further issues with your HVAC systems.


Don’t Sweat It—Call Town Oil

If your air conditioning unit is running but your house still feels like a sauna, don’t wait to have a reliable HVAC contractor fix your system. The longer you run an inefficient system, the more strain you put on it—and the higher your energy bills climb.


Call Town Oil today to schedule a no-pressure AC repair appointment. We’ll restore your comfort with fast, honest service you can count on in Central Connecticut