No Cold Air From AC? Possible Causes Explained

Get Cold Air Back Into Your Home

When your AC is working well, you’ve got it made in the shade. Feeling cool indoors on a hot day is a beautiful thing. 

When it’s not working, your quality of life takes a major hit. Lack of cooling is also a serious health risk during extreme heatwaves. 

A good AC system can last 15-20 years, but it does need to be taken care of. If you notice that your AC is no longer producing cold air, it’s likely just in need of some overdue maintenance

Let’s review how an AC system works—and what might be going wrong when it stops working. 

Possible Causes When There’s No Cold Air From AC

Air conditioning systems are a bit tricky to understand. Cold air can’t really be created. Rather, any form of temperature control involves manipulating the presence of heat. 

Physics teachers sometimes describe it this way: there’s no such thing as “cold”. There’s just the presence or absence of a certain amount of heat. 

So, air conditioners work by removing heat and humidity from indoor air, then circulating the resulting cooled air. 

These are the parts of an AC system that make the magic happen:


  • Evaporator – cooling coils pull heat and humidity out of the air using refrigerant 
  • Blower – blows air over the evaporator to distribute the cooled air 
  • Condenser – hot coils take the heat removed from the air and release it outdoors 
  • Compressor – pumps refrigerant back and forth between the evaporator and condenser coils 
  • Fan – Sends air to the condenser so that heat can be released outdoors
  • Air Filter – Protects the system by removing particles of dirt and dust from the air 
  • Thermostat – Determines how much cold air to distribute 


A minor issue in one of these parts can grind your cold airflow to a halt. 

Here are five common causes for an AC unit that isn’t producing cold air. 

Your AC Unit Is Dirty

Your AC system needs to be clean in order to function properly. If the air filter is soiled and clogged, that restricts airflow moving in, which in turn restricts the system’s ability to deliver cold air inside your home. Or, if dirt builds up on the coils, it creates a barrier between the refrigerant and the air. That makes it harder for the system to transfer heat, and thus harder to produce cold air. 

Air Duct Damage or Blockage

Cooled air travels from the AC unit through a series of ducts before being released through indoor vents. Ducts can become dirty and clogged, preventing efficient airflow. Or they can develop leaks, allowing cold air to escape before it reaches the rooms that you’re trying to cool. 

Refrigerant Leak

When your AC is working properly, it doesn’t lose refrigerant over time. If the refrigerant is being lost, it’s because of leaks. If you see ice crystals around the evaporator coils or if you hear a hissing sound, you likely have a leak. If you detect this problem, turn off your system immediately and contact a professional for a maintenance visit. 

Thermostat Is Set Incorrectly or Is Experiencing an Electronic Error

Sometimes, your AC seems to not be working, but it’s really just a question of easily fixed human error. Check the mode that your system is set to, and be sure you’ve completed all required steps when adjusting the temperature, like hitting ENTER after inputting a change. 

If the system is working but isn’t reaching the right temperature, the thermostat might not be calibrated correctly or may be experiencing an electronic error. In that case, you’ll need to contact a professional. 

Low Power to AC Unit 

Your system might simply be unplugged, or only partially connected to the power supply. Damaged or defective wiring or another utility issue might be to blame if your AC issue is caused by a lack of power. 

What to Do If Your AC Is Not Working

If your AC isn’t working, start with these first steps to get a feel for the scope of your problem:

  • Make sure that electricity is working normally elsewhere in your home
  • Check if cool air is not blowing in your entire home or just part of your home
  • Look for unusual noises or odors

If your AC isn’t working at all and the weather is extremely hot, consider staying elsewhere until your unit can be repaired or replaced. 

Call a professional as soon as possible so that they can come and investigate the problem.

If you’re in the Boise, Idaho area and your AC needs maintenance or replacement, schedule an appointment online with Advanced Heating & Cooling.


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