Why Is My AC Running But Not Cooling?

When your AC unit is running but not cooling your home, it can be a frustrating and uncomfortable experience. At Grayson Air Conditioning, we often see this issue during hot months. Understanding the most common causes can help you diagnose the problem, whether it’s something you can handle yourself or will require a professional.

1. Thermostat Settings or Malfunction

A surprisingly common issue is thermostat misconfiguration. Make sure it’s set to “Cool” and that the fan is set to “Auto,” not “On.” If the fan is on constantly, you might feel airflow without actual cooling. A thermostat that misreads temperature—due to low batteries, improper placement, or outdated hardware, can prevent the system from cycling correctly.

2. Dirty or Clogged Air Filters

Air filters trap dust, pollen, pet hair, and other debris. Over time, this accumulation restricts airflow, reducing cooling efficiency. It also creates conditions where the evaporator coil can freeze, which further restricts airflow and halts cooling altogether.

Tip: Inspect your filter monthly and replace it every one to three months, or more frequently if you have pets or allergies.

3. Blocked or Dirty Condenser Coils

The outdoor condenser unit must expel heat effectively. When coils are covered in dirt, leaves, or debris, heat exchange becomes inefficient, lowering cooling performance. The unit also needs at least two feet of clearance around it to operate properly.

4. Low Refrigerant or Refrigerant Leak

Refrigerant is essential for absorbing household heat and expelling it outside. Low refrigerant—typically caused by leaks—prevents proper cooling. Look for ice buildup on lines or coils, reduced airflow, or hissing noises.

These cases require professional attention. A trained technician must locate and repair any leaks, and recharge the system with the proper type and amount of refrigerant.

5. Frozen Evaporator Coil

If airflow is restricted or refrigerant levels are low, the evaporator coil may freeze. Ice buildup stops the heat exchange process, so the system runs with no cooling. If you spot ice, turn off the unit and let it thaw naturally—then check filters, vents, and refrigerant levels. If freezing recurs, seek expert service.

6. Electrical Issues and Faulty Components

Components like capacitors, contactors, or relays are essential to operate the compressor and fans. When they fail—especially capacitors—the compressor may not start or run properly, leaving the system running but not cooling.

If your outdoor unit doesn’t activate or circuits trip frequently, electrical fault likely is in play. These concerns require a licensed technician for diagnosis and repair.

7. Ductwork Issues and House Envelope

Leaky or poorly insulated ductwork can cause cool air to escape before it reaches your living spaces. Up to 20–30% of conditioned air can be lost through unseen holes.

Problems in ducts or inadequate insulation in attics, crawlspaces, or around vents often cause uneven cooling and higher energy bills. Ensuring proper sealing and insulation improves efficiency and comfort.

8. Undersized or Aging HVAC System

An AC unit that’s too small for your home—or one that’s more than 10–15 years old—may run continuously and still fail to reach the target temperature, especially on hot days. This can lead to high energy use and inconsistent cooling performance.

Replacing an undersized or aging system with an appropriately sized, modern unit can deliver long-term savings and comfort.

What You Can Do vs. When to Call Grayson Air Conditioning When Your AC is Running and Not Cooling

Why Regular Maintenance Matters

Routine maintenance—such as filter replacement, coil cleaning, and thermostat inspection—can prevent most common causes of cool-air failure. Scheduling professional tune‑ups before peak cooling season helps ensure your system runs efficiently and avoids mid-summer breakdowns.

Grayson Air Conditioning Your Local HVAC Company in Mobile, AL

If your AC is running but not cooling, the most frequent causes include thermostat errors, dirty filters, blocked coils, refrigerant issues, frozen evaporator coils, electrical component failures, leaky ducts, and improper system sizing. While basic checks like replacing filters or clearing debris can restore performance, many issues—especially refrigerant or electrical—require trained HVAC service.

At Grayson Air Conditioning, our certified technicians are ready to diagnose these issues, perform professional repairs, and provide maintenance that keeps your system efficient and your home comfortable. Call our team today!