Troubleshooting an AC Blowing Warm Air in Your Home: Causes and Solutions

Homeowners rely on their air conditioners to keep their homes cool during summer. If an a/c is going to have a problem, it will always happen on a hot summer day. One of the most aggravating issues people face is their a/c blowing warm air into the house. Why does this happen?

The main reason an a/c unit blows warm air is clogged air filters. When dust, pet hair, debris, and other particles stick to the air filter, it prevents cool air from getting through. This can easily be fixed by cleaning or replacing them. If this isn’t the problem, it could be caused by wrong thermostat settings or low refrigerant levels.

The last thing you want on a hot day is the air conditioner blowing warm air into your house. Today, we’re going to cover some of the most common reasons this happens. We will also talk about the solutions so you can get the problem fixed today. Read on to learn more.

How Does An A/C Unit Work?

Have you ever wondered how an air conditioner works? Before you attempt to fix an appliance, it’s important that you have a clear understanding of how it functions. Let’s take a look at how an air conditioner is able to provide cool air no matter how hot it is outside.

Before we get into how it works, you should know what the internal parts are. Every a/c unit has 3 important parts:

  • Compressor
  • Evaporator coil
  • Condenser coil

The evaporator coil contains a cooling agent called refrigerant. This is a fluid that’s able to transition from a liquid to a gas and gas to a liquid. As air blows in, it passes along the evaporator coil to get cooled.

In a way, this acts as an air exchange. The a/c is taking the warm air inside your home and blowing it outdoors. In exchange, it replaces that warm air with air that has been cooled down. This keeps your house comfortable on hot and humid days.

So, how do the parts in the air conditioner make this happen? The refrigerant in the evaporator coil travels down to the compressor. In this area, it will convert to a high-temperature liquid. It will then travel to the condenser coil. In this section, the fans will cool it down.

After this stage, the refrigerant gets converted to a cool gas. It then travels to the evaporator coil.

Troubleshooting An A/C That’s Blowing Hot Air

Now that you have a better understanding of how the a/c works, you can find the right troubleshooting method. In this section, we’re going to cover the reasons why this happens and how you can address the problem.

Clogged Air Filters

One of the most common reasons for no cool air is clogged air filters. Over time, the a/c’s air filters can become dirty. However, since this part is out of sight, it’s out of most homeowners’ minds. That’s why they don’t realize how dirty it’s become.

Clogged air filters can cause a number of problems. On top of blowing hot air, they also cause the air conditioner to use a lot more energy. This is why you should always check your air filters first when you think that there’s a problem.

When this happens, the only solution is to change the air filters. With that being said, there is a way to avoid this problem in the future. The a/c’s air filters should be changed every 3 to 4 months while it’s in use.

That isn’t the only thing you should do. It’s also important to keep the air filters clean between replacements. On a bi-weekly basis, you should wash the air filters. You can wash them in a basin with warm soapy water, then allow them to air dry.

Be gentle when washing them. If there is any stuck dirt on the fan, only use a soft cloth to get it off.

Faulty Condenser

A faulty condenser will cause the a/c to blow hot air. Other signs that the condenser is faulty are a fluid leak and loud noises when you turn the a/c on. This is a problem you’ll want to fix asap or else you’ll end up with a very high electric bill.

In most situations, it’s strongly recommended to contact a professional to replace the condenser. You should only attempt to fix it yourself if you’re familiar with the equipment and safety precautions.

There’s something you should consider before replacing the condenser. How old is your a/c unit? If it’s older than 10 years, it’s more economical to replace it. Older a/c units need more repairs. When you factor in the cost of replacing a faulty condenser and other repairs the a/c will likely need over the next few years, it’s better for your budget to replace the unit.

So, how much does it cost to replace the a/c condenser? It can be anywhere from $850 to $300 for just the condenser. When you factor in the cost of the installation, labor, and other parts needed for the job, the price could exceed $4,000.

Frozen Evaporator Coil

Your a/c could freeze trying to keep you cool. The temperature changes inside the a/c unit cause condensation. Moisture from the condensation can freeze on the evaporator coil.

Luckily for homeowners, this is a very easy fix. Here is what you need to do.

  1. Turn off the power to the a/c.
  2. Consult the user’s manual to find out where the access panel is located on the a/c. Open the access panel.
  3. Carefully inspect the evaporator coil for signs of frost and ice.
  4. Keep the access panel open and allow the ice to thaw.
  5. Don’t turn the air conditioner back on until the ice has completely thawed.

Tip: Is it taking too long for the ice to thaw? We understand how difficult is to be patient during a heatwave. To speed up the thawing process, you can use a hair dryer. Make sure the hair dryer is on the lowest setting and that you’re a safe distance from the coil. If you get too close, you could cause damage to the coil.

Dirty Evaporator Coil

Evaporator coils can get dirty which makes it difficult for the a/c to produce cool air. This is because there is a lot of moisture around the coils. Dust and debris can easily get caught in moisture. This causes the evaporator coil to be less efficient and blow warm air.

You will have to inspect the evaporator coil to see if this is the problem. Make sure you turn off the power to the a/c from the circuit breaker before you do this. You can find the evaporator coil by opening the air conditioner’s access panel.

Take a good look at the evaporator coil to find traces of dirt. You can clean off any dirt build-up with a soft bristle brush. To clean the space between the coil fins, use a coil comb. Be very gentle when you do this so you don’t bend the fins.

Homeowners should get in the habit of inspecting the evaporator coil regularly and cleaning it off. This will help to keep the a/c running efficiently.

The Thermostat Is Faulty (Or On The Wrong Setting)

Warm air could be a sign of a problem with the thermostat. There’s also the possibility that you (or another person in your household) adjusted it to the wrong setting. Here are a few things you should do to see if the thermostat is the source of the problem.

  • Check the fan setting. If the blower fan is set to “ON” then it will blow air 24/7 without actually cooling it. Change this setting to “AUTO” so it will run cool settings.
  • Check the batteries. The thermostat won’t be able to send signals to the a/c if the batteries have expired.
  • Make sure it’s not on heat mode. Old thermostats are more likely to run into the issue of not being calibrated correctly. If this is the case, you will need to have it professionally replaced.

Low Refrigerant

Refrigerant is a key ingredient in the air conditioner’s cooling process. If the refrigerant is low or empty, there’s won’t be any cool air. In most cases, homeowners only need to refill refrigerant every 3 to 5 years. Many households can go even longer than that before it needs to be refilled.

While we’re on the subject of refrigerant, there’s one more thing we should address. A refrigerant leak can also cause the a/c to blow warm air. If your air conditioner is under 3 years old, this is likely the case.

A refrigerant leak should always be handled by a professional. If you notice a leak in your a/c, make sure you contact an HVAC professional asap. This is a problem you should never attempt to fix yourself because it’s a health and safety risk.

Malfunctioning Fan

There won’t be any cool air if the fan is malfunctioning. The fan plays an important role in blowing the cool air in and the hot air out. Without a properly running fan, it will feel like the a/c is on a halt.

You will need to inspect the fan to understand why it’s having issues. Make sure you turn off the power to the a/c from the circuit breaker before you attempt to fix it.

One of the first things you should look for is dirt and debris. When debris gets stuck on the fan, problems arise. Use a soft cloth or soft bristle brush to remove dirt from the fan. Don’t use any cleaning agents. However, if dirt is stuck on the fan, you may lightly dampen the cloth with water.

Turn the a/c back on to see if this was the source of the problem. If the fan still isn’t working properly, it’s likely due to a wiring issue. This is something you will need to have an HVAC professional address.

No Power To The A/C

Is there no air coming from the a/c? The power could be disconnected. Inspect the a/c to make sure it’s connected to a power source. If it’s plugged into a working outlet but not receiving power, you’ll need to check the circuit breaker or fuse box.

Check to see if there is a tripped circuit or blown fuse. If either of these is the issue, unplug the a/c and other appliances from that area. This is important because you don’t want to overload the circuit/fuse when you turn it back on.

If the problem is the circuit breaker, you will need to reset it. You’ll notice the handle to the switch has moved to the middle. Turn the tripped fuse switch all the way off then back on again. If the fuse is blown, it will need to be replaced. Make sure you turn the power off to the fuse box from the main switch before replacing it.

How Expensive Is It To Fix The A/C?

There is no set price for fixing an a/c. This is because there are many different things that affect the cost.

The main things that affect how expensive it is are the a/c model and the repair needed. You also need to include the cost of replacement parts in the fix. It’s also important to compare whether you can fix it DIY or need to hire an HVAC professional. If the fix is DIY, you may be required to buy specific tools.

Most homeowners spend between $100 and $610 to repair the a/c blowing warm air. If the repair will cost more than this, it’s recommended to replace the air conditioner. The average cost of a new a/c until is between $3,000 and $8,000. So, why should homeowners replace it?

This is because they will end up spending more on repairs down the road. The cost of a new a/c usually works out to be less than the cost of several repairs and replacement parts needed over the span of 2 to 5 years. The internal parts of an a/c can be expensive. Coils typically cost between $800 and $1,300.

If the problem causing the a/c to blow warm air is minor, the cost of repair is more practical than replacing the unit. Here are some of the costs you could have to cover.

  • Condenser- $850 to $3,000
  • Refrigerant- $50 to $150
  • Fan motor- $75 to $600
  • Labor cost- $75 to $150 per hour

When Is It Time To Call A Professional?

Fixing an a/c can be complicated and dangerous. Even people that are familiar with the tools needed for the job don’t always feel comfortable attempting to fix the problem. You should call a professional for any fix that could put your safety at risk.

HVAC professionals are familiar with how the a/c works, the tools and equipment need for the job, and how to handle the appliance safely. They will be able to troubleshoot the unit correctly and apply the best fix for the problem. On top of that, reputable HVAC professionals will provide a warranty on their work.

Are you wondering whether you should call a professional or attempt the fix DIY? Here are some situations in which you should contact an HVAC expert.

  • Faulty wiring or disconnected wiring.
  • The evaporator coil, condenser, or compressor needs to be replaced.
  • The fan or motor needs to be replaced.
  • A refrigerant leak or other leak that exceeds the regular level of condensation.


It’s always disappointing when your a/c has trouble working. Always address the problem immediately if your a/c is blowing hot air. This is because certain problems we’ve mentioned today can cause further problems with the a/c if they aren’t fixed. They can also cause your electric bill to increase.

Check the air filters when you feel warm air coming from the a/c. If this isn’t the problem, you will need to inspect the evaporator coils, thermostat, and fans until you find the problem. Make sure the power is turned off any time that you inspect key parts of the a/c unit.