You’ve been outside playing with the kids or mowing the lawn in the middle of the brutal summer heat and you head inside to get some cool air and cold glass of water. But the second you step foot inside, the house feels warm. You put your hand up to the nearest AC vent and you feel warm air blowing out. You walk to the thermostat to see if some mistakenly turned on the heat, and you notice that the inside temperature is way warmer than the number you set it to. If this sounds familiar, you are not alone. 

Every summer, Americans experience many of the same air conditioning unit issues. We will tell you about how to address these problems as they arise


Your residential or commercial air conditioning unit is not producing cool air. Instead, a fan is pulling warm indoor air through an air filter and running it over the evaporator coil. The evaporator coil should be full of refrigerant, which is a chemical that absorbs environmental heat and provides cool air once it runs through compressors and evaporators. The air, which should now be cool, is blown out of the vents and into the warm areas of the home or business. 

You may be wondering why the air coming out of your air vents is warm. If the air coming out of the vents is warm, the coil, for some unknown reason, is not properly extracting the warmth from the air. This will be explained in further detail later in the article. Once the refrigerant becomes hot, it should turn into gas and pass through the air compressor. The air compressor is where the hot gas is compressed into an even hotter vapor. Then, that hot vapor should move to the condenser unit where it is then discharged outdoors, allowing the refrigerant to be turned back into a cool liquid and the cycle would start again.  

That all made perfect sense, right? We didn’t think so. That’s why we’ve created a list of the top 7 reasons why your AC unit is blowing hot air.



First, let’s check to see if your thermostat setting is on the mode that says COOL. Next, you should double check that the fan setting is set to AUTO, not ON. This means the fan only rotates when there’s cool air ready to be blown and dispersed throughout your home. And lastly, make sure the temperature is set correctly. If all of these components are set to where they should be, there is likely a mechanical issue with your AC unit.


Due to the chemical makeup of refrigerant, when heat is not absorbed into the coil for a specific period of time, it begins to freeze up. Preventin the presence of hot air around the coil means that airflow is being cut off somewhere in the system. Some possible causes could be: 

  1. Dirty Air Filter: Dirt and debris can sometimes black warm air from entering the return vent. Sometimes even a household object can get stuck in the vent and block the airflow. 
  2. Collapsed Air Duct: Less commonly, you may find that your air duct has collapsed due to poor installation, pests, or wear and tear. This means that it can no longer get the air to travel to the coil.
  3. Dirty Evaporator Coil: Sometimes the evaporator coil gets covered in a layer of build-up, preventing air from passing through. If dirt has found its way into this area, you could have a defective filter or cracks in your air duct.


We already learned how the refrigerant gets hotter when placed under pressure. On the flipside, low refrigerant levels cause the liquid in the coil to expand, cooling it until it’s frozen. Your air conditioning unit is a closed loop system, so when the refrigerant gets low, it usually means the refrigerant line has sprung a leak somewhere. Once the coil has frozen over, the air conditioner can no longer extract the warmth from your home’s air. Instead, it is simply circulated through, unconditioned. 

We don’t recommend trying to fix a refrigerant leak on your own. Call an experienced HVAC technician to perform a “leak search” to find the leak, repair the hole, and add the appropriate amount of refrigerant to the evaporator coil.


The other end of the coil is attached to your outdoor unit, where the refrigerant arrives as a hot vagas and is released to the outdoor air. The box that covers the coil moves the heat outside through vents. Outside AC units can hold up in extreme weather conditions, however sometimes insects, grass, and other debris can make its way to the exposed part of the coil, causing the unit to malfunction.   

If this is the cause of your unit blowing hot air, then it’s important to maintain the area surrounding the condenser box clear of any possible obstructions. Air is always flowing in and out, so it’s a good rule to keep about two feet of breathing room around it. Otherwise, the coil will not perform to its maximum potential.


The compressor is like the heart of your AC unit because it is in charge of circulating the refrigerant throughout the HVAC system. It takes the low pressure gas and turns it into high pressure gas. It requires significantly more electricity to run properly than other HVAC system components. Air compressors tend to use more and more electricity the older they get. If you don’t replace your air compressor in time, there is a chance that it could trip your breaker by pulling too much energy. This could be another reason why your AC is only blowing warm air. Old compressors can begin to gather contaminants that then get settled into the closed loop system. Rust and other metal particles can prevent the refrigerant from working properly.

If you find yourself with a grounded compressor, this means the wiring on the motor has been split or severed in some way, causing a short. You will need to get the entire air compressor or outside AC unit replaced. These types of compressor issues can sometimes be difficult to assess, but FiveStar always gets the job done right.


The fan inside your outdoor unit transfers the heat from the coil outside. When it stops spinning, your condenser can overheat and can shut down. This is a safety mechanism, typically a high pressure switch, that is implemented to prevent any further damage to your HVAC unit. However, this also means that your coil cannot extract the warm air from your home, which would be a clear indicator as to why your AC isn’t blowing cold air. 

The most common issue we see is a burnt-out fan motor that arises from standard wear and tear on your system. Sometimes, the best solution in these situations is to just install a whole new outdoor unit. The fan may be damaged or covered in rust, which can certainly cause it to malfunction.


If your home’s electrical system is outdated, you are running a high risk for blowing a fuse in the middle of summer. Why is that? Well, as we mentioned earlier, older HVAC systems will work harder to meet your cooling requirements and use up too much power to accomplish the desired temperature. Your circuit can become overloaded and if the fuse gets overheated, the whole circuit is disabled. Newer AC models have a circuit panel, rather than a fuse that can be easily tripped when the circuit is overworked. When this happens, you can usually just turn the switch back to the on position. 

Just be sure to monitor the situation closely to make sure it doesn’t happen again, because that would likely mean that there is an internal issue that needs to be assessed. We don’t recommend trying to fix any wiring yourself. Instead, call an experienced FiveStar HVAC technician for help. But you could check to make sure that your air conditioner’s disconnect box hasn’t been switched to OFF. This is located near the compressor (outside) and is the easiest way to manually restrict the power to your AC.


Service and maintenance is needed to keep your air conditioner running properly and preventing it from blowing hot air throughout your home. By putting together a detailed maintenance plan, you can avoid expensive air conditioning issues. It’s always a good idea to call and ask for assistance in air conditioning maintenance, repair, or installation. We always remind our loyal customers to take every precaution even if it means asking questions!

If you live in Middle Tennessee, call FiveStar Plumbing & HVAC at (615) 382-8131 to meet all your heating and cooling needs today!