It’s a frustrating situation. The air conditioner is running. You can hear it, but your home isn’t getting any cooler. Before you assume the worst, know that this is a common problem with several possible causes. Some you can check yourself. Some need a professional. According to ENERGY STAR, leaky or uninsulated ductwork alone can reduce your system’s efficiency by as much as 20 percent, which gives you a sense of how many things can quietly work against your AC even when it appears to be running normally.
Start with the Thermostat
Always check here first. Make sure the thermostat is set to “cool” mode and not “fan only.” Fan-only mode circulates air without actually cooling it, so the system can run all day without lowering the temperature. Also confirm that your set temperature is below the current room temperature. If the display is blank or unresponsive, replace the batteries.
Check the Air Filter
A dirty filter is one of the most common reasons an AC underperforms. When it gets packed with debris, airflow across the evaporator coil gets restricted, which is the part that allows the system to pull heat out of your home’s air. Severe restriction can also cause the coil to freeze over entirely. Check your filter monthly during summer and replace it if it looks dirty. Our post on cleaning air filters and HVAC systems walks through what to look for.
Low Refrigerant
Refrigerant is what makes cooling actually happen. It absorbs heat from inside your home and transfers it outside. If there’s a leak, your system loses cooling capacity and runs longer while doing less. Signs include the system running constantly without reaching your set temperature, ice forming on the indoor or outdoor unit, or a hissing sound near the refrigerant lines. Be aware this is not a DIY fix. Handling refrigerant requires a certified technician.
Frozen Evaporator Coil
If the evaporator coil ices over, the system can’t exchange heat properly. This usually happens because of restricted airflow. Dirty filters, closed vents, or blocked return air registers are the most common culprits. If you notice ice on any part of your system, turn the AC off and let it thaw completely before restarting. Then address the airflow issue so it doesn’t happen again.
Ductwork Problems
Leaky ducts send conditioned air into your attic or crawl space instead of into your living areas. Disconnected or crushed duct sections can block airflow to certain rooms entirely. If some rooms in your home cool well while others stay warm, ductwork may be the reason (and not the unit itself).
When It’s Time to Call
If you’ve checked the filter, thermostat, and vents and the problem continues, it’s time to call a professional. Refrigerant leaks, coil problems, and duct issues all require trained hands and the right equipment. If you’re also noticing warm air blowing from your vents, rather than just weak cooling, our post on why your AC is blowing hot air covers that situation in more detail.
If your AC is running but your home still isn’t cooling down, give us a call. We’ll find the problem and get your system back on track before summer really heats up.