How to fix aircon not cooling

We’ve all been there. Sweating through a sleepless night...or slogging through the heat of a sweltering July afternoon. It’s no fun when your air conditioner is not cooling, but it can happen. And when it does, it’s not going to be in the dead of winter. It’ll be the hottest day of the summer, and no matter how many times you turn down the thermostat you still find the AC not blowing air that is cold enough.

Air conditioning systems are more than just the condenser unit (the AC unit or heat pump) sitting outside your home. Typical split-system air conditioners have a lot of moving parts, including an indoor air handler unit (furnace or fan coil), an evaporator coil, air filter, thermostat and copper tubing (refrigerant lines) that connect the indoor and outdoor units. So there are a number of answers to the question “Why is my air conditioner not cooling the house?” But fear not. Just because your system isn’t cooling, doesn’t automatically mean expensive AC repairs or replacing the entire system.

Most homeowners can do some basic troubleshooting and may be able to resolve the issue. However, there are also times that you’ll need to make the call to your local Carrier® dealer for professional air conditioner service.

Why is the AC Not Blowing Cold Air?

From very simple issues like a thermostat set incorrectly or a dirty filter...to a more complex situation that requires replacing components...there are a wide variety of reasons why you may find your air conditioner running, but not lowering the temperature in the house. We’ll outline some items you should check before calling a professional here. For a little more detail, visit our troubleshoot an air conditioner page. 

Thermostat is Set Incorrectly

When you notice your home getting a little hotter than normal, first check the thermostat settings. Be sure it is set to cool. If the thermostat is set to cool, check the temperature setting to be sure someone hasn’t changed it. If it is off, set to heat, or set for constant fan (sometimes simply labeled “on”), switch it back to cooling operation. After the system kicks on, wait a few minutes, then check for cold air blowing from the registers. If it’s cold, problem solved! If not, move on to the next troubleshooting tip – checking the air filter.

Dirty Air Filter

Your AC system may include an air filter located in or around the indoor air handler unit. The filter catches dirt, dust and other airborne particles as they enter the air handler unit. It keeps the components inside the system cleaner and operating more efficiently and can help keep the air in your home cleaner as well. A dirty air filter can block airflow and reduce cooling to your home. In more extreme cases it can cause the system to shut down completely. 

If your thermostat checks out and you still don’t have cool air, locate your system’s air filter, turn the system off, remove the filter and inspect. If, after you are satisfied that you have a clean air filter and your central air conditioner does not cool your home, you’ll have to dig a little deeper to locate the problem.

Condenser Unit is Blocked

As previously described, your central air conditioning system likely includes an outdoor condenser unit. The exterior of the condenser unit features a large outdoor coil, which wraps most of the way around the outside of the unit. The coil includes a series of thin metal “fins” which are spaced very tightly together. If your air conditioner is running, but not lowering temperatures inside, one issue could be a blocked or clogged condenser coil. When operating correctly, the condenser fan draws air into the outdoor unit through the condenser coil to pull heat energy out of your home. Dirt, grass and other airborne debris can accumulate between the fins, clogging the coil. A dirty coil can lead to reduced energy efficiency, lack of cool air from the registers, or in extreme cases, complete system shutdown or damage to the compressor from overuse. You can attempt to clean the coil by clearing away debris, carefully vacuuming the coil with a brush attachment or rinsing gently with a hose. If your system still isn’t cooling, it’s probably time to call a pro. 

Damaged Heat Pump

In some cases, your outdoor unit might be a heat pump. A heat pump looks just like an AC unit, with some different components inside that allow it to both cool and heat your home. In cooling operation, it operates just like an air conditioner system’s condenser unit and is subject to the same issues – dirty, clogged coil, frozen coil, refrigerant leaks, compressor malfunctions, etc. If your heat pump system isn’t cooling, check thermostat settings, the air filter, and the condenser unit for previously described issues. If everything checks out and you’re still sweating inside, call your local HVAC dealer. 

Evaporator Coil is Frozen

The indoor component of your central air conditioning system will include an evaporator coil. If your indoor unit is a furnace, the evaporator coil sits in its own cabinet, outside the furnace. If the indoor unit is a fan coil (typically as part of a heat pump system), the evaporator coil sits inside the fan coil cabinet. Warm indoor air passes through the evaporator coil where heat energy and humidity are removed from the air. Cooler, more comfortable air is then circulated back to your home. Signs of a frozen evaporator coil include:

• Frost forming on the copper refrigerant tubing coming from the coil cabinet
• Inadequate cooling
• Higher utility bills
• Excessive condensate drainage near your indoor unit
• In extreme cases, frost forming on exterior refrigerant tubing or the outdoor unit

Because accessing the evaporator coil is difficult, resolving issues associated with a frozen evaporator coil are best handled by an HVAC professional.

Refrigerant Leak

Refrigerant is a chemical that is critical to the cooling process. It flows through the system’s indoor and outdoor coil, changing from liquid to gaseous form, drawing heat energy and humidity from indoor air and releasing it outside. Depending upon its severity, a refrigerant leak can contribute to your AC system not blowing cold air, your system may run for longer periods of time without adequately cooling your home, or it can cause a damaged or failed compressor and complete system shutdown.

Checking and resolving issues involving refrigerant levels in your system is another job for your local Carrier dealer. 

Undersized Air Conditioner

Air conditioners are “sized” according to the amount of cooling they can provide as measured in BTUh (British Thermal Units per hour). Under moderate conditions, you may not notice any issues with an undersized air conditioner. However, as temperatures rise outside, your AC may run for long periods of time and struggle to keep you cool. 

You might be able to determine the size of your AC unit from the rating info on the cabinet panel, but it will be difficult to determine whether it is the “right size” for your home. There are a number of factors involved in sizing a system for your home, including square footage, quality of construction and insulation, local climate, and more. 

If your system is undersized, it may be possible to provide cooling in problem areas by adding a ductless unit to help out in “hot spots”. Or, it may be better to replace the system with one that is correctly sized. The best way to address sizing issues is to contact a qualified HVAC professional who can accurately assess your home and its optimum cooling capacity.

Contact a Carrier HVAC Dealer

Thermostat not reaching the set temperature? If you reach this conclusion and you’ve exhausted the options outlined previously, it’s time to call a Carrier HVAC dealer. It’s important for your comfort, but also for the health of your AC system. Continuing to run your AC when it’s not properly cooling your home can take a minor issue and turn it into a major component failure or system replacement.

My AC Is Running But Not Cooling the House

Do you have an air conditioner in your home? For millions of people in the United States, they depend on these cooling systems to help push through the summer months. As the temperature continues to climb as summer moves forward, homeowners are preparing to fight the elements.

While people are focused on buying new AC units, tuning up their systems, and participating in air conditioning maintenance, others are dealing with AC repairs and system issues. As there are a wide variety of air conditioning problems out there, an air conditioner not cooling is one of the most problematic. If you’re experiencing an air conditioner running but not lowering temperature, you may be confused and frustrated. Luckily, there are a few ways to troubleshoot the issue.

Keep reading to learn some simple steps for trying to fix this annoying problem.

Why is my air conditioner not cooling the house?

Unfortunately, there are many reasons why you have AC running but not cooling your home. In fact, the issue could be found with your thermostat, filter, or with another critical system component.

While you can always call an AC service provider to diagnose and treat the issue, there are a few troubleshooting tips you can try first.

These easy-to-follow tips include:

Check the thermostat

If you have HVAC running but not cooling, the first step is to check your thermostat. First things first, make sure this device is set to cool. If it is, check the temperature setting to see if anyone made an adjustment. If you recently had AC service, something could have been changed by mistake. In the event the thermostat is set to off, switch it to heat before changing it back to cool. After waiting a few minutes until you hear the cooling unit kick on, head to your registers to check for any cold air blowing out. If you feel the cold, the problem is fixed! If you don’t, move onto the next step.

Examine the air filter

While it may sound like a surprise, a dirty air filter can significantly impact your cooling system. That said, it’s best to consistently check to see if these are dirty, then replace them if needed. While your air filter’s job is to trap dirt, dust, and other airborne particles, they can’t work properly if they’re filled with debris. As an air filter helps to keep these particles out of your home, they also aid in preventing this debris from infiltrating your system’s components.

If you have central AC not blowing cold air, take a look at your air filter. But before checking it, make sure your system is powered off. From there, remove the filter and take a look. If everything checks out and the filter looks clean, proceed to the next troubleshooting tip.

Look at the condenser

A central air conditioning unit typically has an outdoor condenser unit. The outside of this unit usually features an outdoor coil that wraps around the condenser. This coil has multiple “fins” that are spaced close to one another. If you're experiencing AC not cooling while the system is powered on, you could have a clogged or blocked coil. Unfortunately, a wide variety of debris can find its way into this equipment, including grass, dirt, and other contaminants. This can result in a serious clog, which can lead to a system malfunction. While this can cause your unit to blow warm air instead of cold air, it can also decrease your energy efficiency and even result in a system shutdown.

To troubleshoot the issue, check the condenser and clean away any debris. This area can be cleaned by a vacuum with a brush attachment, or try using a hose to gently wipe away any dirt and grime. Still dealing with AC running but not cooling? If so, it may be time to call a professional for service.

Frozen evaporator coil

On the indoor portion of your AC unit, you’ll find an evaporator coil. When warm air passes through this coil, heat and humidity are removed from the air, then much cooler, conditioned air is then pumped back into your home. But on some occasions, this coil can freeze, which can result in your central AC not blowing cold air.

Look out for these signs of a frozen evaporator coil:

• Poor, ineffective cooling
• Increase in energy bills
• Frost accumulating on the copper refrigerant tubing
• Excessive condensate drainage

Unfortunately, fixing a frozen evaporator problem can be very challenging. That said, you’ll want to call a licensed, experienced HVAC technician to solve the issue. If you have an air conditioner not cooling, these professionals can sometimes fix the problem within minutes.

Leaking refrigerant

In order for your AC unit to work properly, refrigerant is needed. This is a chemical that flows through both your indoor and outdoor systems. The primary goal of refrigerant is to extract the heat and humidity from the indoor air before it goes outside. If you have a refrigerant leak, this can result in poor system performance and even a complete unit shutdown.

While it may sound simple to check and fix your refrigerant issue, this is another job for a dependable HVAC technician. They can easily check your refrigerant levels and make any necessary adjustments.

Leaky ducts

Your ducts are another location where a leak may be present. As your air ducts are used to guide conditioned air throughout your home, a leak can throw a kink in the process. As many AC ducts are found in the attic, some of that warm air can travel into your ductwork, leading to an increase in indoor temps.

As repairing leaky ducts can be a serious hassle, call a professional AC service provider for assistance.

If your air conditioner is working but not cooling, try these tips to restore cooling comfort to your home!