With spring officially here, our air conditioners are shaking off the dust and gearing up to keep us cool as temperatures start to rise. But sometimes, an AC might not function as expected. One troublesome issue you might encounter is an AC blowing hot air. There are a few different reasons this may happen. Let’s take a look at how this problem may come to be and what you can do to fix it. 


How Does an AC Work? 

An air conditioner doesn’t actually create cool air – it pulls warm air from the home into a filter and passes it over an evaporator coil. The coil is filled with a special chemical called refrigerant. The refrigerant turns from a gas to a liquid in the compressor and then cycles inside to absorb the heat as it evaporates. Rather than “creating” cool air, this process eliminates heat from the air. Now this air is at a lower temperature and it can be distributed back into the home. 

When hot air is blowing out of an AC, something in this process isn’t working properly. With so many components at play within the air conditioning process, it can be a number of problems. But ultimately it boils down to one central issue: for whatever reason, the cooling coils are not being allowed to absorb heat. Let’s see why that might be. 


Reasons Why Your AC Might Be Blowing Hot Air 


Issue With Thermostat 

Before you attempt to troubleshoot anything else, be sure to double-check your settings on the thermostat. This may seem like a ridiculous cause but you never know if someone accidentally set your system to heat. It could also be a wiring issue. 

If your AC is set to anything higher than room temperature, it will blow warm air back into your home. Simply adjusting the setting should solve the issue. 

If you just installed a new thermostat or AC unit, the culprit may be poor wiring. Improperly wired thermostats can result in unusual behavior with your AC unit. Be sure to have a professional inspect it to make sure everything is wired correctly. Getting all the connections in order should solve the problem.

Note that poor wiring issues only occur with newly installed systems. If your system was working fine and the issue emerged seemingly out of nowhere, there is another underlying cause. 


Low Refrigerant

Refrigerant is the key ingredient in a functioning AC unit. One of the most common issues that can cause heat to blow from an AC is a leak in the refrigerant line. If there isn’t enough refrigerant -also sometimes referred to as freon- the substance won’t be able to properly turn from liquid to gas. That means the cooling coils won’t be cool enough to absorb heat from the air. 

The refrigerant line is a closed system. You will never have to add more freon to the system for it to work properly if there are no issues within the system. If freon levels dip, that points to a leak somewhere in the line. 

If your system is low on refrigerant, call in an HVAC professional to help repair the leak and replenish the freon levels. This is not a project you should attempt to DIY unless you have professional experience in AC repairs.  


Clogged Air Filter 

Lowered airflow is another issue that may lead to an AC blowing hot air. It’s vital for your system to have an unobstructed path while distributing air throughout the home. A clogged air filter can drastically reduce proper airflow. This will lead the rest of your system to overcompensate and potentially overwork itself. 

It’s crucial to stay on top of air filter replacements. You should strive to replace your air filter at least every 6 months. Some households may need to replace their air filters even more frequently if they have pets or allergy issues. If you wait too long to replace them, they will get dirtier and dirtier eventually leading to a clog. If your system is blowing hot air as a result, the issue should resolve itself when you switch out the filter. 


Loss of Compression 

Freon can’t do its job unless it’s converted to a liquid before it’s sent into the evaporator coil. If the compressor isn’t functioning properly, the whole process comes to a halt. When an AC unit experiences a loss of compression, the refrigerant won’t be able to undergo full expansion and it won’t properly cool the coils. 

Unfortunately, compressors are very complicated to fix. It’s best to cut your losses and replace this component when it stops working. Be sure to consult your trusted HVAC technician to be sure that this is the source of the issue and they should be able to replace it promptly. 


Issues With Power Supply 

Power supply issues are another issue that may cause your AC to blow hot air. It could either be a blown fuse or tripped amp breaker. Both of these scenarios are likely the result of a dated electrical system or outdoor AC unit. Older systems may require too much power to function and could easily blow a fuse on a hot day. 

When something does go awry with your power supply, the fuses and amp breakers will attempt to protect your AC from electrical surges. This can inevitably lead to your AC not functioning properly. 

Luckily, this issue is easily fixable. If the amp breaker is to blame, simply turn off the AC, let it rest for 30 minutes, and reset your breaker. If you blew a fuse, start by opening the disconnection box to expose the wires. Now use a voltmeter to assure there is power running to your system and to confirm which fuse is blown. Once you’ve confirmed this information, turn off the breaker, stop the current from flowing into the fuse, and replace it. 

Remember, both of these issues likely have underlying causes to address. Have an HVAC professional inspect your entire system to check for trouble areas. 


Frozen AC Coils 

This may seem counterintuitive, but frozen AC coils are a common culprit when a system starts blowing out hot air. Sometimes your system won’t provide the evaporator coil with enough warm air. When heat isn’t properly absorbed into the refrigerant, it may freeze. This will compromise the entire process and the hot air from inside your home will circulate without being cooled. 

There are a few reasons why this may occur. A dirty filer might block warm air from entering the system. It could also be the result of a blocked or collapsed air vent. And finally, an AC coil might freeze if the evaporator is covered in a thick layer of grime. Call an HVAC professional to get to the bottom of this issue. 


Do You Need HVAC or Plumbing Help?  

To the T Plumbing and Heating is Thorton, Colorado’s trusted professionals for all your HVAC and plumbing needs! Whether your AC is blowing out hot air or you just can’t seem to unclog your bathroom sink, we are here to help with any and all emergencies 24/7! Get in touch with us to learn more about how we can help solve your challenges.