You just had a new air conditioner installed, and it’s not cooling your home properly. This frustrating situation is more common than you think, and the good news is that most causes are fixable.
Common Reasons Your New AC Isn’t Cooling
Refrigerant Issues
The most frequent culprit is improper refrigerant charge. Your installer may have undercharged or overcharged the system during installation. Both scenarios prevent proper cooling. Low refrigerant means insufficient heat absorption, while overcharge causes compressor strain and reduced efficiency. This requires a certified technician to measure and adjust the refrigerant to manufacturer specifications.
Incorrect Thermostat Settings
Check your thermostat first. It should be set to “cool” mode, not “fan” or “heat.” The temperature setting should be lower than your current room temperature. If you have a programmable thermostat, verify it’s configured correctly. A thermostat installed in direct sunlight or near heat sources will give false readings and prevent proper cooling.
Airflow Problems
Restricted airflow is a major issue with new installations. Your air filter might be dirty or installed backwards. Check that all supply vents are open and unobstructed by furniture or curtains. The outdoor unit needs at least two feet of clearance on all sides. If the installer left protective packaging or debris around the condenser coils, this blocks airflow and prevents cooling.
Electrical Connection Errors
Incorrect wiring during installation can cause the system to run without actually cooling. The outdoor unit might not be receiving power, or the reversing valve on heat pumps could be wired incorrectly, causing it to heat instead of cool. You’ll notice the outdoor fan running but the compressor staying silent, or vice versa.
Wrong Size Unit
If your AC is undersized for your space, it will run constantly without reaching the desired temperature. Oversized units cycle on and off too frequently, failing to dehumidify properly and making your home feel clammy. Proper load calculation before installation is critical, and this mistake requires replacing the unit.
Ductwork Issues
New AC installations sometimes reveal existing ductwork problems. Disconnected ducts, large leaks, or crushed flex duct lose cooled air before it reaches your rooms. If your installer modified ductwork during installation, poorly sealed connections waste cooling capacity. You might hear rushing air sounds or notice certain rooms staying warm.
Installation Mistakes
Brand new systems can have installation errors like kinked refrigerant lines, which restrict flow. The condensate drain line might be improperly pitched, causing water backup and system shutdown. Some installers forget to remove shipping blocks from compressor mounts, creating vibration and efficiency problems.
What to Do Right Now
First, verify your circuit breakers are on and the thermostat batteries are fresh. Check that your air filter is clean and properly installed. Make sure all vents are open and the outdoor unit has clear space around it.
If these basic checks don’t solve the problem, contact your installer immediately. Most HVAC companies provide installation warranties that cover these issues. Document the problem with photos and temperature readings from different rooms.
Don’t attempt refrigerant repairs yourself. These require EPA certification and specialized equipment. Running a malfunctioning AC can cause compressor damage, turning a simple fix into an expensive replacement.
Prevention for Future Installations
Choose licensed, insured contractors with good reviews. Ask about their installation process and whether they perform load calculations. Request a post-installation check that includes refrigerant charge verification, airflow measurement, and thermostat calibration.
A properly installed air conditioner should cool your home to the set temperature within a few hours of starting. If yours isn’t performing as expected, addressing the problem quickly prevents equipment damage and keeps your home comfortable.