Why Is My AC Running But Not Cooling?
Published January 22, 2026 • 5 min read
It's a frustrating scenario: your AC is running, you can hear it humming away, but your house isn't getting any cooler. Before you panic, let's walk through the most common causes—some you can check yourself, and others that need professional diagnosis.
Check These First (DIY)
1. Your Air Filter
A clogged air filter is the #1 cause of AC problems we see. When the filter is dirty, airflow is restricted, causing the system to work harder and cool less effectively. Check your filter—if you can't see light through it, it's time to replace it.
2. Thermostat Settings
Make sure your thermostat is set to "COOL" (not "FAN" or "OFF") and the temperature is set below the current room temperature. Also check if the batteries need replacing—a dead thermostat battery can cause all sorts of issues.
3. Vents and Registers
Walk through your home and make sure all vents are open and not blocked by furniture, rugs, or curtains. Closed or blocked vents can significantly reduce cooling performance.
Common Causes (Need a Technician)
Refrigerant Issues
If your system is low on refrigerant, it can't absorb heat effectively. Low refrigerant usually means there's a leak somewhere that needs to be found and repaired. We never just "top off" refrigerant without identifying the source of the leak.
Frozen Evaporator Coil
If you see ice on your indoor unit or the copper lines going to it, you have a frozen coil. This is usually caused by low airflow (dirty filter) or low refrigerant. Turn your system off and let it thaw before calling for service.
Dirty Condenser Coils
Your outdoor unit needs to release heat. If the condenser coils are covered in dirt, leaves, or debris, heat transfer is reduced. You can gently hose off the unit, but be careful not to bend the fins.
Capacitor or Electrical Issues
Capacitors help start and run the motors in your AC. A failing capacitor can cause the compressor or fan motor to run inefficiently or not at all. This requires professional diagnosis and replacement.
When to Call a Professional
- You've checked the filter, thermostat, and vents but it's still not cooling
- You see ice on any part of your system
- The outdoor unit isn't running at all
- You hear unusual noises (grinding, squealing, banging)
- Your energy bills have spiked unexpectedly
How We Diagnose AC Problems
At Crazy Comfort, we don't guess. We systematically test each component and document our findings with photos sent directly to your phone. You'll see exactly what we see before we recommend any repairs.
Our diagnostic fee is $129, which gets applied to the repair if you proceed. No hidden fees, no surprise charges.
AC Not Cooling? We Can Help.
Same-day service available in Katy, Fulshear & surrounding areas.