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AC Blowing Hot Air

Why is my AC Blowing Hot Air?

Air conditioners are made specifically for blowing cold air around your house.

But, over time, you may notice that your AC goes from blowing cold air to blowing hot air.

So what do you do when your AC is blowing hot air? Why is it even happening?

Read on to find out!

How Air Conditioners Produce Cold Air

First things first: before you can understand why there is warm air coming from your air conditioning unit, you should first get to know how an AC system produces a cool breeze.

Of course, common knowledge can tell you that an AC system works by removing heat from your home’s air.

But you need to understand the specifics of this process, as well as become familiar with the different parts of the AC system, so that you can understand how things can begin to malfunction.

An AC unit produces cooled air through the following process:

  • The fans inside the AC unit blow warm air over the evaporator coils.
  • The refrigerant liquid inside the coils goes through the expansion valve and evaporates.
  • The evaporation of the refrigerant absorbs heat, turning the warm air to cold air.
  • The compressor then pressurizes the refrigerant gas so it turns back into a liquid.
  • The pressurization creates heat, which is dispersed through condenser coils in the outdoor AC unit.

This process repeats over and over again to create cold air to maintain a low temperature in your house.

So if your AC unit starts blowing hot air, this means that something is going wrong at one or more steps in the process.

Why Is My AC Blowing Hot Air?

Now that you understand how an air conditioner works, it’s time to become familiar with the possible causes of AC problems.

In general, the most common causes of an air conditioner blowing warm air are the following:

  • Dirty evaporator coils
  • Malfunctioning outdoor unit
  • Clogged air filters
  • Refrigerant leak
  • Thermostat settings
  • Faulty compressor
  • Duct leak

Each issue has its own potential causes and solutions, since moving parts can easily become damaged or faulty over time.

To explain each issue thoroughly, we have divided them into separate sections below.

  1. 1. Dirty Evaporator Coils

    An air conditioner blowing warm air is often the sign of dirty evaporator coils.

    As we detailed above, evaporator coils play an important part in the process of producing cold air because they help the refrigerant absorb heat from a room and evaporate into a gas.

    However, over time, evaporator coils can collect dust and other debris that are drawn in by the fans.

    If you don’t regularly have them cleaned, the dust can build up to the point that the warm air from the room doesn’t come into contact with the coils.

    This means that the refrigerant won’t be able to absorb the heat from the warm air, which means it won’t be able to evaporate and produce cold air.

    Luckily, there’s an upside to this issue, if it’s really the cause of your AC problems. It’s easy to fix!

    All you need to do is clean each dirty evaporator coil so that there’s no more debris getting in the way of the heat transfer.

    If you’re familiar with your air conditioner, all you have to do is open it up and wipe each evaporator coil with a soft cloth.

    However, if you’re not confident with your ability to safely clean your air conditioner, it’s best to hire a professional maintenance service.

  2. 2. Malfunctioning Outdoor Unit

    Another possible cause of your AC blowing warm air is a malfunctioning outdoor unit.

    Your AC outdoor unit can take various forms, depending on what kind of HVAC system you have, but many air conditioning systems have heat pumps.

    There are several ways your outdoor unit can malfunction.

    The first is that the circuit breaker has been tripped. An easy way to tell that this is the cause of the problem is by observing if the entire outdoor unit isn’t functioning at all.

    If you suspect this is the problem, simply reset your circuit breaker.

    The second is that there is a blown fuse, which can happen when your air conditioner is old and has to work overtime to blow cool air on a hot day.

    The fuse can get blown when your air conditioner struggles to get enough electricity, which overheats the fuse and disables the circuit.

    If you think this is the problem, double check if your air conditioner has a circuit panel or disconnect box (usually found near the compressor in the outdoor unit). If it does, simply flip the switch back on.

    Finally, the third is that your air conditioning system is being obstructed – perhaps by debris, plants, or other objects.

    If your air conditioning system is being obstructed, it won’t be able to dissipate the heat created by the compressor. Debris may also clog its ducts and cause it to overheat and malfunction.

    To fix this, simply clear the area around your outdoor unit.

  3. 3. Clogged Air Filters

    This is a simple but very important thing to check: whether your AC unit has clogged air filters or not.

    Although a dirty air filter may seem too small to cause your AC to blow warm air, it has more of an impact on your air conditioner than you may think.

    Air filters are what maintain the indoor air quality. They do this by filtering out dust, pathogens, and other particles that may irritate your nose.

    However, as you can imagine, these filters eventually catch so much dirt that they become clogged. And when an air filter is clogged, it’s harder for air to flow through them.

    This can restrict airflow within your AC unit. Thus, you get an AC blowing hot air.

    The airflow restriction can also affect your AC unit in other ways, and might prompt other issues to arise.

    Luckily, this is one of the easiest issues to fix. All you need to do is change out your air filters (if they’re disposable), or clean the dirty filters (if they’re reusable).

  4. 4. Refrigerant Leak

    One of the most dangerous causes of an AC blowing warm air is a refrigerant leak, which you may be able to observe if you have frozen evaporator coils.

    Refrigerant levels are important to maintain because a certain amount of refrigerant is needed to go through the expansion valve, evaporate, and cool the air in a room.

    So, if you have low refrigerant levels, there may not be enough refrigerant going through the expansion valve, and you get an AC blowing hot air.

    Since the refrigerant line is a closed loop system, the only way you can have low refrigerant levels is if there is a leak!

    And if your AC unit is leaking refrigerant, this can also be harmful to the environment since refrigerant contains chemicals that aren’t naturally found in most ecosystems – so it’s doubly concerning.

    If you suspect your AC unit is leaking refrigerant, it is best to hire professionals to handle the repair, rather than fiddle with something you don’t understand.

  5. 5. Thermostat Settings

    Another possible cause of your AC blowing hot air is its thermostat settings.

    As you know, the air temperature of the cool air your AC is blowing depends on the temperature indicated in the thermostat settings.

    However, sometimes the thermostat setting will say that it’s set to a certain temperature, but the temperature of the air that your AC is blowing is obviously different.

    It may be that your AC just needs some time to get the temperature up, especially if it’s an older model.

    However, if you notice the temperature is still way too high after a few cycles, then it may be that your thermostat is glitching.

    The best way to fix this is to contact professionals who know how to handle electronics.

  6. 6. Faulty Compressor

    A faulty compressor is one of the hardest issues to observe, but it can lead to your AC blowing hot air.

    If your AC compressor is no longer working, it won’t be able to pressurize the evaporated refrigerant so that it turns back into a liquid.

    A fully functioning AC compressor should be able to create high pressure gas. A faulty AC compressor, on the other hand, may only be able to create low pressure gas or no gas at all, causing the AC to produce less cool air.

    The best way to have this fixed is by contacting professionals.

  7. 7. Duct Leak

    Finally, the last possible cause of your AC blowing warm air is a duct leak.

    If your home’s ductwork has any leaks or holes, then the cool air produced by your AC may not even be able to reach the room.

    If you’re familiar with your AC ducts, you could try patching up any leaks by yourself. However, if you’re not sure of your capabilities, it’s best to contact a professional.

What Do I Do If My Air Conditioner Is Blowing Warm Air?

So what do you do if your AC is blowing hot air?

In general, your best bet is to contact an HVAC professional.

A good HVAC technician will have all of the knowledge, experience, and skills to get your AC back to blowing cold air.

Book Your Appointment with One Stop Heating and Air Conditioning Now!

And if you’re looking for an experienced HVAC technician, look no further!

Here are One Stop Heating and Air Conditioning, we have teams of technicians with years of experience.

So what are you waiting for? Book an appointment on our website using our Service Form!


(801) 355-9500

  • Emergency AC Repair
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Service Areas

Wasatch Front, UT, and surrounding areas

Main Office

611 W 9560 S Suite E, Sandy, UT 84070

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