No matter how well you care for your air conditioner, you’ll eventually run into problems where it may run but not cool the air. This does not always mean that your system has a substantial problem, however. This guide explores the fundamentals of how your AC works and the seven common reasons it’s not cooling your home along with top solutions.
Air Conditioning 101
Air conditioners are carefully calibrated mechanical systems. At their most basic level, they transfer heat from one space to the next and circulate air.
How Refrigerant Works
Most people identify the refrigerant in an air conditioner as the cause of its cooling capability. However, most homeowners don’t understand how the refrigerant cools a home’s air as well.
The refrigerant cycles between high pressure and low pressure. When the pressure decreases at the evaporator coil, the refrigerant gets cold and absorbs heat from the air moving through the system. Conversely, the refrigerant pressure increases at the outside unit, causing it to get hot and vent the heat it absorbed inside.
Airflow’s Critical Role
While the refrigerant transfers heat from one place to another, it cannot work without sufficient airflow. Inside your home, the warm air has to flow over the evaporator coil. As it does, the cold refrigerant flowing through the coil absorbs the heat, cooling the circulating air before pushing it through the vents.
Outside your home, the system has another refrigerant coil called the condensing coil. The refrigerant running through this is hot, allowing it to vent the heat absorbed inside. However, the outdoor unit needs air moving over the condensing coil to vent the heat.
At both coils, a fan moves the air over the coils. For air to move effectively, not only must those fans run properly, but the coils must remain free from obstructions.
Why Your AC May Not Produce Cool Air
An air conditioner blowing warm air indicates a problem with transferring heat or circulating air. The following issues can inhibit heat transfer or restrict airflow. Recognizing the problem and learning how to troubleshoot can help you identify problems earlier so that you can get your air conditioner back on track as soon as possible.
1. Thermostat Issues
One of the most common and easiest to solve issues is the thermostat. Thermostat issues can range from improper settings to an old or malfunctioning thermostat.
Start by checking that the fan is set to Auto rather than On. When the thermostat is set to On, the fan will run constantly, even without the compressor running. Consequently, the air coming from the vents may feel warmer than it should when the compressor is running.
Most thermostats should last 10 to 15 years, after which the sensors may not work properly. If your thermostat is more than 10 years old, consider replacing it with a digital programmable model.
Finally, check the mode setting on your thermostat. To initiate the compressor, make sure the mode is set to Cool.
2. Compressor Doesn’t Have Power
Another common problem is system power. Many homes have separate circuit breakers for the indoor and outdoor units. Some outdoor units have additional power disconnects. Check both to ensure the unit is receiving power.
If the system is running but is not producing cool air, the power problem could be isolated to the outdoor condensing unit.
3. Airflow Restrictions
Without air flowing through both the indoor and outdoor units, it cannot produce cool air. Restrictions can result from obstructions and mechanical problems.
The easiest obstruction to check is the air filter, which needs replacing every 30 to 90 days for 1- and 2-inch models. To prevent an obstruction at the air filter, plan to check it every month and gently vacuum the intake side to help extend its life.
Something may also be physically obstructing the air intake, either inside or outside the unit. The outside unit should have at least 2 feet around it and 5 feet above it, clear and free from obstructions. Clearance needed for inside air returns depends on the size of the vent, so talk to your maintenance tech for their recommendations.
Fans that are not running properly cannot circulate sufficient air. Routine air conditioner maintenance is the best way to determine fan operation. During this process, a technician will test the fan motor and clean the fan assembly.
4. Insufficient Refrigerant
Your system must have sufficient refrigerant to transfer heat effectively. Insufficient refrigerant prevents it from increasing the pressure enough to vent the heat it absorbs. Additionally, low refrigerant can cause the system to freeze, which can also cause warm air to flow from the system.
Insufficient refrigerant typically results from a leak somewhere in the system. The easiest way to check your system’s charge is routine testing, which is included with annual professional maintenance. If the technician finds low refrigerant, they can look for the leak and recharge the system, though most companies charge a fee for these additional services.
5. Faulty Compressor
The compressor condenses the system’s refrigerant as it flows into the condensing coils, allowing it to vent the heat it has absorbed. When that compressor fails to work properly, it doesn’t build sufficient pressure to heat the refrigerant. Symptoms of a faulty compressor include frozen condensing coils, unusual screeching or other sounds or failure to initialize altogether.
A professional must address a faulty compressor, which commonly requires replacing the outdoor unit. A technician will test the compressor during routine AC maintenance, ensuring it builds sufficient pressure.
6. Dirty Refrigerant Coils
The refrigerant coils hold the cold and hot refrigerant, facilitating the heat transfer process. However, both the indoor and outdoor coils get dirty over time. When they do, that dirt acts as insulation, inhibiting heat transfer.
To prevent this, the coils require periodic cleaning. The outside coil is easy to clean, using a garden hose without a spray nozzle to prevent damage. Cleaning this once or twice a season is usually sufficient to avoid buildup.
The indoor evaporator coil is a little more complex to maintain. Located within the indoor unit. This means you must access it, which can void a warranty if your unit is still covered. Additionally, with its indoor location, you cannot simply rinse it with a hose. Washing it by hand can risk damaging the coil, causing expensive repairs. A professional can clean it safely and effectively without risking your warranty.
7. Undersized Air Conditioner
If the warm air started after replacing the system or completing a home renovation, you may have an undersized unit. Undersized units cannot absorb enough heat to effectively cool your home. Additionally, they’ll commonly run much longer cooling cycles, exponentially increasing energy consumption and accelerating wear on the system.
Find the Fix to Your AC Problems with Our Help
For more than 70 years, property owners around Layton have trusted Smedley Service to keep their homes comfortable. Our team provides expert heating and AC repair, maintenance and installation along with indoor air quality solutions. Call to schedule a service or maintenance visit with one of our NATE-certified technicians today.
