Home Air Conditioner

Why is My AC Blowing Hot Air? (Overview Image of AC and 10 Possible Reasons)

Why is My AC Blowing Hot Air? (Overview Image of AC and 10 Possible Reasons)

Isn't it frustrating when you try to survive the heat wave and your AC is only blowing hot air?

It's enough to make you want to scream! Especially when the weatherman has been promising us a reprieve from the heat and humidity, and your AC is blowing hot air instead of cool. You might be tempted to give up on your AC and through it out of the window. But don't despair! There are things you can do to get your AC blowing cold air once again.

The three most common issues why your AC is blowing warm air are:

  • the air conditioner’s refrigerant levels are low
  • the air conditioner's filter is dirty
  • the air conditioner coils are dirty

If these are not the issue, below are also some other common issues why your AC might be blowing hot air.

Safety Caution: Do not try to fix AC, electricity, or refrigerant issues if you're not a certified professional. Always consult and hire an AC professional to fix your AC.

Disclaimer: This is not a DIY guide. Only for informational purposes. Always read your AC manual and follow AC professionals' advice. 

What Parts Does an AC Consist Of?

Overview of AC's (Air Conditioner) Parts and How it Works

Before we try to find why your AC isn't working, we need to know the basics on how the AC works in the first place. In order for an air conditioner to work, it needs a few key components:

  • Refrigerant: The refrigerant is what absorbs and removes heat from the air. 
  • Compressor: Heats the refrigerant and moves it between the condenser and evaporator.
  • Condenser: Gets rid of the heat from the refrigerant, turning it into liquid form.
  • Evaporator: Its coils takes in heat from the air, cooling it down.
  • Expansion valve: Controls the flow of refrigerant into the evaporator and releases pressure of refrigerant.
  • Reversing valve: Only included if the AC is also made for heating. In the winter, it reverses the flow of refrigerant so that it goes through the condenser and evaporator in opposite directions.
  • Thermostat: Measures the temperature of the outgoing refrigerant and adjust the incoming refrigerant's pressure based on the users desired temperature settings.
  • Blower: Pushes the air through the evaporator coils, helping to cool down your house.
  • Fan: Cools the warm refrigerant that runs in the outside unit's condenser.
  • Filter: Is located in the inside unit. Filters out dust and other particles from the air that passes through it.

The refrigerant is what actually cools your home. It is a fluid that circulates through the system while being compressed and decompressed, removing heat from the air in your home as it moves through the system. The evaporator coil is where this happens: when refrigerant runs over this coil, it absorbs heat from the surrounding air, cooling it down.

The condenser, meanwhile, is where the refrigerant is heated back up and turned into a gas. This compressed gas then moves to the compressor, which pressurizes it even more so that it can be circulated through the system.

So if your AC isn't working, there may be several different possible causes and we've listed the most common ones here below.

10 Common Reasons AC is Blowing Warm Air

Looking our overview image on How Does AC Work we can see that the inner air conditioner unit's evaporator should run cold refrigerant in it's coils and then transfer the collected heat outside. If your AC is blowing hot air, there is a problem with the refrigerant not getting cold enough for some reason. Let's dive into the possible issues that can cause refrigerant not getting properly set up.

1. The air conditioner’s refrigerant levels are low. 

A common problem that can cause an air conditioner to blow warm air is low refrigerant levels. Refrigerant is a fluid that is used in air conditioning to help cool the air. When the refrigerant levels are low, it can cause the AC to blow hot air instead of cool air. There are several reasons why refrigerant levels may be low. 

One possible reason for low refrigerant levels is a leak in the system. If there is a leak, then the refrigerant can easily escape from the AC system and it will not be able to cool the air effectively. A professional technician should check for leaks to make sure that the refrigerant levels are not low because of a leak.

Another possible reason for low refrigerant levels is simply the age of the air conditioner. AC systems do not last forever, and it is quite common for older air conditioners to have problems with their refrigerant levels. If the air conditioner is old or outdated, then it may be time to replace it with a newer, more energy-efficient model.

If you are having problems with your air conditioner blowing hot air, then the first thing that you should do is check the refrigerant levels. A professional technician can help you determine whether low levels of refrigerant are causing the problem and will make any necessary repairs.

2. The expansion valve is not working properly

Another common cause of an air conditioner blowing hot air is a problem with the expansion valve. The expansion valve is responsible for controlling the flow of refrigerant into the evaporator and releasing pressure from the refrigerant as it passes through. If this valve is not working properly, then it can affect how well the AC system functions.

The expansion valve is located between the condenser and evaporator coils and is usually located near the evaporator coil. If you notice that your AC unit is blowing hot air, it's important to have a technician check the expansion valve to see if it needs to be replaced. Otherwise, you may continue to experience problems with your AC unit.

3. The air conditioner filter is dirty. 

The filter on your AC unit is responsible for removing contaminants from the air before it enters the unit. If the filter is allowed to become dirty, it will restrict airflow and cause the unit to overheat. In order to prevent this from happening, make sure to regularly clean or replace the filter on your AC unit.

By keeping the filter clean, you can help to ensure that your AC unit runs smoothly and efficiently. Regular filter maintenance can also help to extend the lifespan of your AC unit. So don't forget to give your filter a little attention every now and then!

4. The air conditioner coils are dirty. 

The coils on your AC unit play an important role in regulating the temperature in your home. These coils help to transfer heat from inside your home to outside of it. If these coils become dirty, they will become less effective at transferring heat and may cause the unit to overheat and start blowing warm air.

To prevent this from happening, make sure to regularly clean the coils on your AC unit. If allowed by the AC seller, you can do this yourself by using a brush or vacuum attachment to remove dirt and dust from the coils. Alternatively, you can hire a professional to clean the coils for you. Either way, making sure to keep the coils on your AC unit clean will help to keep your home cool and comfortable all summer long.

5. The vents are blocked. 

One of the most important things to do for your HVAC system is to make sure that the vents are clear and unobstructed. If there are objects blocking the vents, it can prevent airflow and cause the unit to overwork itself and blow hot air. This not only makes your home uncomfortable but also puts unnecessary strain on the system, which can lead to costly repairs.

To avoid these problems, be sure to remove any objects that may be blocking the vents. This includes furniture, rugs, curtains, and anything else that could potentially get in the way. By taking this simple step, you can help ensure that your HVAC system runs smoothly and efficiently all year long.

6. The air conditioner is not receiving enough power. 

If your AC unit is not receiving enough power, it will not be able to function properly and may start blowing hot air. This could be due to a problem with the electrical circuit that the AC unit is plugged into, or it could be due to a problem with the AC unit itself.

If you suspect that this is the problem, you should check the circuit breaker and make sure that the AC unit is plugged in correctly. You should also check for any loose wires that may be causing an interruption in the power supply.

7. The air conditioner is not properly sized for the space. 

An air conditioner that is too small for the space it is trying to cool will have to work overtime in order to achieve the desired temperature. This can cause the unit to overheat and start blowing hot air instead of cold air. To avoid this problem, make sure to choose an AC unit that is the proper size for the space you are trying to cool.

The size of the unit is measured in British Thermal Units (BTUs) per hour. To calculate the BTUs needed to properly cool space, you will need to know the square footage of the space and the climate. Once you have this information, you can consult a BTU chart or calculator to determine the proper size for your needs. With a properly sized AC unit, you can enjoy cool, comfortable air all summer long without fear of overheating.

8. The thermostat is set too high. 

Kinda no-brainer, but if your air conditioner also has heating function, one of the first things you should check is the thermostat. If the thermostat is set too high, the air conditioner will run continuously in an attempt to reach the desired temperature, which can cause it to blow hot air. Lowering the thermostat to a more reasonable temperature setting will help prevent this from happening.

9. There is excessive humidity in the room. 

The air in a room can feel heavy and oppressive when the humidity levels are high. Not only is this uncomfortable, but it can also cause the air conditioner to overwork itself in an attempt to cool down the space. Using a dehumidifier is an effective way to reduce humidity levels and make the room more comfortable.

Dehumidifiers work by drawing moisture out of the air and collected in a water tank. This helps to reduce the amount of moisture in the air, making it feel cooler and easier to breathe. By reducing the humidity levels in the room, you can help to prevent mold and mildew growth.

10. The outdoor unit is dirty. 

Over time, dirt and dust can accumulate on outdoor units, just as they do indoors. This can interfere with the unit's ability to function properly, causing it to run less efficiently and potentially leading to problems.

As such, it is important to clean the unit off as needed, removing any dirt or debris that has accumulated. If allowed by the seller of AC, this can be done with a brush; simply remove the dirt and debris, taking care not to damage the unit. With regular cleaning, you can keep your outdoor unit functioning properly for years to come.

What is AC (Air Conditioner)?

An AC, or air conditioner, is a device that controls the temperature and humidity of the air in homes and other buildings. There are several different types of AC, including window units and portable units for room cooling, mini-split central units for whole-home cooling, heat pumps for all-season heating, and ductless mini-split systems for areas where ducting is not feasible.

Different air conditioners have different features and functions, so it’s important to research the models that best suit your needs before making a purchase. AC units are available for sale at many home improvement stores, professional AC installment companies, and on online retailers.

In order to install an AC, you need to hire a professional that is certified to install the specific brand and model that you have chosen. For most central unit installations, a technician will drill holes into your walls and floors to fit the ductwork for your AC. Window units are typically easier to install, as they simply sit in your window frame and require no additional drilling or work on your part.

Find Your AC Professional to Fix AC Issues

It's frustrating when an air conditioner blows only warm air, but please also consult and hire a professional to fix any technical AC issues. Please call your local AC professional and ask for their suggestion on how to get your AC blowing warm cool air again.

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