Few things are more frustrating than coming home to a house that's stuffy and warm only to find your air conditioner is running. The system sounds like it's on, the fan is blowing, but the air coming out of the vents isn't cool. This is one of the most common AC complaints we hear from homeowners in Gwinnett County, and it has a range of possible causes — some simple, some more serious. At Henson Heating Air and Plumbing, we diagnose and fix this problem every day. Here's a breakdown of what to check and what might be going on.
Start Here: The Simple Checks
Before assuming the worst, there are a few quick things worth checking yourself. These won't always be the answer, but they're fast and free to rule out.
Check Your Air Filter
A clogged air filter is one of the most common reasons an AC runs but doesn't cool effectively. When the filter is dirty, it restricts airflow across the evaporator coil, which prevents the system from absorbing heat properly. Check your filter — if it's grey and caked with dust, replace it and give the system 30 minutes to see if cooling improves. Filters should typically be changed every 1–3 months depending on your home and household.
Check Your Thermostat Settings
Make sure your thermostat is set to "Cool" mode and not "Fan Only." When set to fan only, the blower runs continuously but the system isn't actually cooling the air — it's just circulating it. Also check that the set temperature is actually lower than the current indoor temperature. If it's set to 74 and your home is 74, the system won't run a cooling cycle.
Check the Outdoor Unit
Walk outside and look at your condenser unit. Is it running? If the fan isn't spinning or the unit is completely off while your thermostat is calling for cooling, that's a sign of an electrical issue — often a failed capacitor or a tripped breaker. Also check that nothing is blocking airflow around the unit. Debris, overgrown shrubs, or objects placed too close to the unit can reduce efficiency significantly.
More Likely Culprits When the Simple Checks Don't Help
If the filter is clean, the thermostat is set correctly, and the outdoor unit is running but the house still isn't cooling, you're likely dealing with one of the following issues.
Low Refrigerant
Refrigerant is the substance your AC uses to absorb heat from inside your home and release it outside. If your system has a refrigerant leak, the refrigerant level drops and the system loses its ability to cool effectively. Signs of low refrigerant include: the air coming from vents is slightly cool but not cold, ice forming on the refrigerant lines or evaporator coil, and a hissing sound near the indoor or outdoor unit. Low refrigerant is never a DIY fix — it requires an EPA-certified technician to locate the leak, repair it, and recharge the system. If your refrigerant is simply "low," it means there's a leak that needs to be addressed. Refrigerant doesn't just evaporate over time.
Frozen Evaporator Coil
Your evaporator coil is located inside the air handler and is responsible for absorbing heat from the air in your home. When airflow is restricted — from a dirty filter, blocked vents, or low refrigerant — the coil can get too cold and freeze up. Ironically, a frozen coil means warm air coming out of your vents because the ice is acting as a barrier between the air and the cooling surface. If you suspect a frozen coil, turn the system to "Fan Only" mode for a few hours to let it thaw, then replace your filter and try again. If it keeps freezing, there's an underlying cause that needs professional attention.
Dirty Condenser Coils
The condenser coils in your outdoor unit release the heat that was absorbed from inside your home. When these coils are caked with dirt, grass clippings, or debris, they can't release heat efficiently — which means the system keeps cycling warm refrigerant back into the house. This is a common issue in Georgia where outdoor units get dirty quickly from grass, pollen, and general outdoor grime. Cleaning the condenser coils is part of a professional AC maintenance visit and can make a noticeable difference in cooling performance.
Failing Compressor
The compressor is the heart of your AC system — it's what pressurizes the refrigerant so the cooling cycle can work. A failing compressor may still run but lose the ability to maintain proper pressure, which results in the system blowing air that isn't cold. Compressor issues are on the more serious and expensive end of the repair spectrum. If your system is older and the compressor is failing, it may be more cost-effective to replace the system than to repair it — especially with financing options available through Henson Heating Air and Plumbing.
Oversized or Undersized System
Sometimes the issue isn't a breakdown at all — it's that the system was never the right size for your home. An oversized system cools too quickly and shuts off before it can properly dehumidify the space, leaving the home feeling clammy and uncomfortable even if the temperature reads correctly. An undersized system runs constantly and still can't keep up. If your AC has always struggled to cool properly and the system is relatively new, it's worth having a load calculation done to verify the equipment is properly sized.
When to Call for AC Repair
If you've gone through the basic checks and your AC is still running but not cooling, it's time to call a professional. Most of the causes above — refrigerant leaks, frozen coils from underlying issues, dirty condenser coils, failing compressors — require proper equipment and training to diagnose and repair correctly. Delaying the call usually makes things worse and more expensive.
Henson Heating Air and Plumbing provides AC repair service throughout Loganville, Lawrenceville, Duluth, Conyers, Covington, Lithonia, Stone Mountain, Decatur, Oxford, and all of Gwinnett County. We offer 24/7 emergency service for situations where you can't wait — a Georgia summer with no working AC is a real emergency, and we treat it that way.
We service all makes and models and install Daikin and Carrier systems when replacement makes more sense than repair. Financing options are available so you're never stuck making a rushed decision based on budget alone.
If your AC is running but your home isn't cooling down, call Henson Heating Air and Plumbing or request service online. We'll diagnose the problem fast and get your system back to cooling the way it should.
