Why is My AC Not Cooling? How to Fix? [With Pictures]

If you've been running your AC all day and night and still feel like you're living in an oven, this post is for you! You have an AC not cooling, it's hot, and you're not getting the cool air you need. Suddenly, you're stuck in a sweltering house with no relief in sight! So what can you do if your AC isn't cooling? Read on to find out the most common causes of why your central AC might not be cooling, how to fix them, and how to avoid them in the future. Stay chill folks!

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How Air Conditioner Works

The air conditioner is a device that extracts heat from inside your home and transfers it outside, helping you stay cool during hot weather. It starts with the process of refrigerationRefrigerant is a chemical that changes from liquid to vapor as it absorbs and expels heat energy. Your air conditioning system uses refrigerant to extract the heat from inside your home and release it outdoors. This is what allows you to have cold air circulating throughout your home.

How does this happen?

The warm indoor air is drawn into the return vent, passed through a filter, and blown over the evaporator coil. The refrigerant cycles through the evaporator coil absorbing the heat from the air, turning the refrigerant from liquid to gas. Once the air is cooled, it is blown back into the house.

Next, the refrigerant travels to the compressor within the outside unit, which increases the refrigerant's temperature. When the super hot vapor refrigerant reaches the condenser, it passes through the condenser coil and releases the heat outdoors. As the refrigerant cools, it changes from a gas back to a liquid. It is now ready to go through the cycle again the next time you turn your thermostat down.

What To Do If You Have An AC Not Cooling

Several things can be done if your air conditioner isn't cooling. We'll discuss them before we tell you what may have cause your AC to stop working properly.

First: Check Your Thermostat

Make sure the thermostat setting is on "cool" and that the desired temperature is lower than what is currently present in this room. Next, try changing the batteries if that doesn't work, especially if the thermostat screen is malfunctioning.

thermostat set to cool

For additional information, you can check out our blogs on thermostats not reaching their set temperature and thermostats not working at all.

Second: Assess The Circuit Breaker

circuit breaker

Next, assess that the circuit breaker is set correctly. Many circuit breakers have a separate breaker for the indoor and outdoor AC units. Make sure all the switch settings are correct. 

Third: Clear Any Obstructions To Airflow

The consequences of poor air flow are devastating. A dirty air filter restricts proper airflow, which in turn prevents heat from being transferred out of your home. Not to mention, dirty air filters can make your AC air smell musty and create extremely bad indoor air quality conditions. So if your AC is not cooling, try changing your filter. And check out our guide to HVAC filter changeouts if you want to learn more about this.

Dirty, clogged filter

Also, make sure to remove any objects blocking vents and ensure all your vents are open. Closed or blocked vents contribute to poor airflow, especially when there is a dirty air filter in place.

Fourth: Check Your Disconnect

See that box mounted near the outside AC unit in the picture below? That's called the disconnect box. An AC disconnect is a safety feature that can shut off the electrical circuit. An HVAC technician will also use the disconnect to cut power when conducting an AC repair or AC service.

AC disconnect box

AC disconnect box

Check to see if the disconnect power is shut off. If so, turn it back on. Also, observe if the connections in the disconnect box come loose or burn up. If you find damaged or faulty wires in your disconnect box, you will need an AC repair.

AC Disconnect Switch inside AC Disconnect Box

AC Disconnect Switch inside AC Disconnect Box

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Why AC Is Not Cooling

AC Has Low Air Flow

Your AC isn't cooling, huh? Well, your thermostat states your AC is on and you feel cold air from the vents, but your HVAC system just cannot keep up. If your AC is not cooling, yet you feel low air flow from the vents, there may be an issue with air flow. Keep reading to find out the biggest causes of low cool air flow.

Clogged Filter

When your HVAC filter is dirty or clogged, this seriously compromises your air flow. A dirty filter will prevent enough indoor air from passing into your HVAC system and over the indoor evaporator coil. If air flow is restricted, then heat transfer is inhibited. Without the proper amount of air passing over the indoor evaporator coil, your HVAC system will struggle to cool your home. 

Filthy Evaporator Coil 

Dirty-mold-indoor-coil-Baltimore-st- 153KB 500 by 666 pixels (1)

The evaporator coil is typically located inside the indoor unit above the furnace and facilitates heat transfer from the indoor air to the refrigerant flowing through it. When hot air is drawn in through the return vents, it is pushed over the indoor coil. The refrigerant flows through the indoor coil and absorbs the heat from the indoor air blown over it. Over time, the indoor coil becomes dirty, clogged, and moldy. In some circumstances, a frozen evaporator coil is the cause of your AC not cooling. The buildup of filth and debris inhibits heat transfer from the air to the refrigerant. The refrigerant will freeze when air flow is limited, and your AC will not deliver cold air.

Bad Indoor Fan Motor

If the AC is not cooling, you may have a dirty indoor fan. The indoor fan pulls hot air into the AC unit, and if it's dirty, it won't be able to pull in enough air to cool your home. An HVAC specialist removes the cover during an AC service call and uses a brush or vacuum cleaner to clean off all the dirt and dust from the indoor fan. Once the fan is clean, it can efficiently cool your home.

To learn about more causes, check out our blog about AC fans not working.

AC Not Cooling, But Blowing Warm Air

You AC is on but you feel room temperature air flowing out of the vents. Where is the refreshing cold air?!?! Keep reading to find out why the air conditioning unit is not pushing out cold air.

Bad High Voltage Wire

The high voltage wire signals the AC condenser unit to turn on. If the high voltage wire is loose, disconnected, damaged, or faulty, your AC unit will not turn on. When your AC condenser unit does not turn on, your AC will be unable to cool your house. Since the indoor unit is on and the outdoor unit is not, your AC will push out room temperature air. 

Faulty Compressor


AC compressor

The AC compressor is necessary for pressurizing the refrigerant and pushing it through the AC system. If the compressor malfunctions, the refrigerant will not transfer heat, resulting in your AC not cooling. Therefore, the AC unit will continue to push out room temperature air.

You can get more information about causes for your AC compressor not working by checking out our compressor failure blog.

Dirty Condenser Coil 


If your air conditioner isn't cooling, there's a good chance that there's a problem with your outside unit. The condenser coil wraps around the outdoor ac condenser. When the refrigerant passes through the outdoor coil, the heat from your home is released outdoors. However, the outdoor coil accumulates dirt, debris, and filth due to regular use and outdoor conditions, restricting critical heat transfer. When the AC cannot release heat, your AC system will not be able to cool your home. 

Broken Capacitor

AC Capacitor

If your air conditioner is not cooling, the problem may be with the capacitor. A capacitor stores electrical energy and releases it when needed to start the motor. When a capacitor fails, it will prevent the outside AC unit from starting up and cooling your home.

Malfunctioning Contactor 

AC Contactor

One common issue that can prevent your A/C from cooling is a bad contactor. A contactor is a device that helps to turn your AC unit on and off. A closed contactor allows electricity to flow to the compressor and outdoor fan motors; an open contactor prevents electrical current flow. If it becomes damaged or corroded, it can prevent the AC condenser unit from starting up. This can cause your home to become extremely hot and uncomfortable in the summer months.

Faulty Condenser Fan Motor 


When the fan or fan motor is faulty, the AC will not be able to effectively transfer heat outside your home. The condenser fan converts hot refrigerant gas into cool liquid by blowing air through the condenser coil. When this happens, the refrigerant releases the heat outdoors. If the condenser fan motor is not working, your AC cannot cool your house.

Bad Outdoor Disconnect

The disconnect box is located near the outdoor condenser unit. If the wires in the disconnect are loose, damaged, or burnt, your air conditioning unit will be unable to cool your home.

Incorrectly Charged Refrigerant

Refrigerant is essential to the cooling process. If your AC refrigerant is low, it becomes less pressurized, which prevents heat transfer. Low refrigerant results from a freon leak, which means you need an AC repair. Many air conditioning systems use the refrigerant R-22 Freon, which is has been recently banned. Find out what this means for your AC in our blog about R-22 freon.

Thorough & Efficient AC Repair

Tips on staying cool this summer!

Your AC will function at its best if it is maintained in top condition. Regular maintenance will ensure your air conditioner is in good working order for when the heat hits. Regular AC maintenance / service helps to prevent common air conditioner problems. During an AC tune-up, an HVAC specialist will evaluate all requirements for proper air flow, check your refrigerant, and assess each mechanical component. Because of routine maintenance, you won't have to worry about a bad capacitor, low voltage wire, or other AC repair issue disrupting your breeze!

Chill & Comfortable All Summer.....

If your AC unit isn’t cooling like it should, don’t panic! There are a few things you can check to try and get your system up and running again. Make sure the filter is clean, the thermostat is set to cool, and the power is on. If you’ve tried all of these things and your AC is still not working, it's time to call SuperTech - Baltimore's best AC company. Summer temperatures can be brutal, so don’t wait until the last minute to take care of this problem. Stay cool this summer by keeping your AC unit in good shape!

Call today or schedule online today here to ensure a cool and comfortable summer!

  • This explanation provides a clear overview of how the cooling process works in an HVAC system. It starts with warm indoor air being drawn into the return vent, passing through a filter, and cooling over the evaporator coil. This coil absorbs heat, causing the refrigerant to change from liquid to gas. Once the air is cooled, it’s circulated back into the house.

    The refrigerant then moves to the compressor outside, where its temperature is increased. When the hot vapor refrigerant reaches the condenser, it releases heat outside, converting back from a gas to a liquid. This cycle repeats each time you adjust your thermostat, illustrating the efficient way in which HVAC systems.

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