Why Your AC Is Running But Not Cooling Your House

It's 90°F outside, your AC is running nonstop, and your house is still hot. This is one of the most common HVAC complaints during North Carolina summers. Here are the most likely causes.

Check These First (DIY Fixes)

1. Dirty Air Filter

The #1 cause of AC performance problems. A clogged filter restricts airflow, causing your system to work harder while cooling less. Check your filter right now.

2. Thermostat Settings

Make sure it's set to "cool" (not "heat" or "fan only") and the temperature is set lower than current room temp. Set fan to "auto" rather than "on."

3. Blocked Vents

Walk through your house and make sure all supply and return vents are open and not blocked by furniture.

4. Dirty Outdoor Unit

If it's covered in leaves, grass clippings, or dirt, it can't release heat efficiently. Clear debris and gently hose it down.

Causes That Need a Professional

5. Low Refrigerant (Leak)

If your system is low on refrigerant, it physically cannot cool your home. Signs include ice on refrigerant lines, hissing sounds, and lukewarm air. Refrigerant doesn't get "used up" — if it's low, you have a leak.

6. Frozen Evaporator Coil

Turn the system off and let it thaw, then call a technician to find the root cause.

7. Failing Compressor

The heart of your AC system. If it's failing, the system runs but won't effectively cool. This is typically the most expensive repair.

8. Ductwork Leaks

Duct leaks can waste 20-30% of your cooled air, especially in unconditioned spaces like attics or crawlspaces.

9. Undersized System

If your AC has never adequately cooled your home, it may be undersized for your square footage.