AC Blowing Hot Air? (Common Reasons Plus How To Easily Fix It)

HVAC professionals receive the highest number of calls regarding ACs blowing warm air during summer.

This is the most common HVAC problem, and you can sometimes resolve it by yourself. So if you are thinking, why is my air conditioner blowing hot air? This guide will help you understand the most common causes and how you can solve them.

AC Blowing Hot Air

Why Is Your AC Blowing Hot Air? (Causes & Fixes)

If your air conditioner is blowing hot air, do not worry; here are some of the most common reasons for your AC blowing hot air:

Incorrect Setting Of Thermostat

If hot air is coming out of your air conditioner, your thermostat might have been accidentally set to ‘heat’ mode.

In this case, the fix is relatively easy on your own. Just flip your thermostat’s setting to ‘cool’ and check whether your air conditioning unit starts to blow cold air again.

In addition, you must ensure that your thermostat’s batteries are in working order and the temperature is not set to a higher setting.

Remember that the ‘auto’ function will only utilize the fan when air is cooled or heated. But if you tap ‘on,’ the fan will run continuously, circulating the air inside, even if your heater or AC is off.

Experts recommend that you mainly use the ‘auto’ function and only switch to the ‘on’ mode when required.

Outdoor Unit Lost Power

In a split AC system, both the outdoor and indoor components must run in tandem to complete the cooling cycle and supply cold air inside your home.

That is why, if the outdoor unit power supply is interrupted, only the indoor components are working, causing warm air to blow from the vents in your home.

Make sure that your outdoor unit has power. You can do it by checking and verifying if your air conditioner’s breaker has tripped or not; reset it if required.

Also, look at the ON/OFF switch near or on your outdoor air conditioning unit to ensure it is ON.

A power loss in your outside unit may lead to various problems inside the vents. Therefore, checking the emergency shut-off switch and circuit breaker are the ideal things to do at this point.

Remember, if you constantly check the circuit breaker, you might face some serious electrical problems. In this case, get in touch with an HVAC technician as soon as possible.

AC Is Low On Refrigerant

Another reason for your AC unit blowing hot air might be refrigerant leaks. The AC unit does not receive enough charge to complete the cooling cycles when the refrigerant is escaping your air conditioning system through a leak. Therefore, your indoor air might feel warmer than average.

A low refrigerant level is quite a common reason for the air conditioning units to blow warm air; however, it is one of those problems that you cannot fix by yourself.

You will need professional help from a certified and licensed technician to figure out the problem and solve it. For example, if your AC refrigerant is not leaking, it might be a leak in the air ducts.

Some other signs that point to a refrigerant leak in your air conditioning unit include:

  • Hissing noises from components of the air conditioner
  • Frozen evaporator coils
  • High electricity bills

Related Article How To Check The Freon In AC

AC Evaporator Coil Is Dirty

Dirty evaporator coils might also be why your air conditioner is blowing hot air. The main reason behind that is dirty air filters.

Even though you can replace your air filters yourself, you will have to hire a professional to clean your evaporator coil.

The evaporator coil in your air conditioner extracts heat from the inside air to initiate the cooling process.

Condensation is a by-product of this entire process; that is why most air conditioning units have a condensate drain and drip pan to catch moisture and expel it out of your air conditioning system.

AC Evaporator Coil Is Dirty

You can check for this problem by shutting down your AC system power and opening the access door to interior system parts; this helps you assess evaporator coils.

If you observe ice or frost on coils, the ideal option is to provide thawing time. This process might take around 24 hours based on the freeze severity.

Related Article How To Clean Dirty AC Coil

Clogged Filters

Even though air filters are not directly related to air temperature; however, a dirty air filter may result in a dirty evaporator coil.

When your evaporator coil is clogged with debris and dust, there might not be the right amount of airflow needed for proper cooling operation.

In addition, a clogged and dirty air filter might lead to debris build-up, which may cause your evaporator coils to freeze.

We know what you might be thinking, doesn’t frozen coils mean cool air, but the reality is that frozen coils hinder cool airflow, leading to your AC blowing hot air.

Therefore, based on the climate, your household, and filter type, replace your air filter every 30 to 60 days.

Related Article How To Change An AC Filter

Clogged Expansion Valve

An expansion valve’s job is to efficiently release the refrigerant liquid and then expand it to gas. Unfortunately, whenever this expansion occurs, it sends literal ‘chills’ all over your cooling coils.

This is what cools the coils. But if your expansion valve is not properly working, the cooling coils will not be cooled down because the refrigerant will not expand it to gas.

Therefore, it will lead to your home AC blowing hot air while running. You can solve this problem by unclogging them, though it is easier said than done.

You might need some help from a professional HVAC technician. Once the clog is cleared, you will observe that the refrigerant cycle returns to normal, and your AC will not blow warm air anymore.

Preventing Your AC From Blowing Hot Air In The Future?

You may have understood the leading causes of hot air coming out of your air conditioner and how to fix them, but what can you do to prevent your air conditioner from blowing hot air?

Here are certain things you can do to prevent your AC from blowing hot air:

  • Keep the thermostat at 78°F when you are at home and around 7-10°F higher when you are away
  • Use the ceiling fan to feel 4° cooler
  • Have proper ventilation to prevent moisture problems
  • You can also sign up for a home maintenance plan, so you remember tune-up appointments annually
  • Also, set reminders to check the air filter every month
  • Keep the windows and doors closed while running the AC unit
  • Regularly dust and clean your house
Prevent AC From Blowing Hot Air

Why Is My LG Portable AC Blowing Hot Air?

Sometimes your LG Portable AC might blow hot air but do not worry; we have compiled here the reasons why it might be happening and how you can fix those issues:

  • Air Filters: Your LG portable AC’s air filters might clog up a few times a year. Clean them using warm water and mild detergent, and when dry, put them back.
  • Vent Issue: Often, a filthy vent also leads to warm air. Again the solution is simple, ensure that the vent hose is installed correctly and then clean it with warm water and detergent.
  • Condensates: There might be excess water in your condensate drain if you live in a humid area. You can fix it by draining the drain pan often.

People Also Ask (FAQ)

How much does it cost for a technician to fix an AC blowing hot air?

If your air conditioning unit is blowing hot air, you can expect to pay anywhere around $167-600 for a technician to check out the situation and address it. However, based on the extent of your repairs, you might be paying upwards of $450-1000.

Should I turn the AC off if it is not cooling?

Yes, if your air conditioning unit is not cooling, there is one thing that you must do. Turn it off and call your HVAC service provider as soon as possible; so they can take a look at the problem.

Why is my AC not reaching a set temperature?

Your AC might not be reaching a set temperature due to clogged air filters, poorly ventilated houses, and high humidity. In addition, your AC cannot completely dehumidify your home and reach a set temperature.

How long does it take for AC to drop 1 degree?

For a typical 3 to 4-bedroom house, it would take around three hours for an AC to drop a single degree. If it takes longer than that, and your home is not near the required temperature, there might be an issue with your air conditioning unit.


There are various reasons why your air conditioner is blowing hot air, and even though, for portable units, you can deal with most of the problems by yourself.

However, a central air conditioning unit requires the hands of a certified professional. Hopefully, this guide was able to help you identify any probable causes for your air conditioner blowing hot air.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.