Why is My Central Air Conditioner Blowing Hot Air?

June 09, 2014

Oh man, this is the last thing you wanted. It’s heating up outside in the Kansas City area, and your air conditioner is blowing hot air in your face. 
 
What could be the problem?
 
Here are 3 common issues—2 are easy to fix.

1) Wrong thermostat setting

OK, we know this sounds silly, but please make sure your thermostat is set to “cool” not “heat.” 
 
You never know, someone (your child, your child’s friend, a resentful house guest) may have changed it by mistake.
 
Also, make sure the thermostat is set to “Auto” not “On.” If it’s set to “On” the blower will run constantly—even if the air isn’t being cooled. So that’s why it might blow cool air sometimes and warm air other times.

2) Dirty condenser unit

The condenser unit is the outside A/C unit with the big fan. To understand why it being dirty would cause your air conditioner to blow hot air, you need to know how an air conditioner works.

 
Here’s the Cliff Notes version. 
 
Your typical central air conditioner has 2 units: the condenser unit (outside) and the evaporator unit (inside). A refrigerant line connects these two units.
 
Basically, your air conditioner‘s inside unit absorbs the heat from your air using refrigerant and blows the now cooled air throughout your home using a duct system.
 
That refrigerant flows to the outside unit to release all the heat it has absorbed. Then refrigerant flows back inside to absorb more heat from your air.
 
But if your outside unit is covered in dirt, leaves, grass, and who knows what else, then it can’t release the heat properly. And that means the refrigerant can’t absorb more heat to cool the air. 
 
So that’s why your air conditioner may be blowing hot air!
 
If your unit is dirty, you can either clean it yourself, or have a professional clean it properly as part of a regular air conditioner maintenance visit.  
 
Leaves and whatnot are easy to clean off. But the condenser coils (tubes that the refrigerant flows through) need a special coil cleaner to properly get the dirt off. 

3) Low refrigerant

Like we said before, refrigerant absorbs the heat from your air and transfers it outside (that’s why it’s called a “heat transfer fluid”). But if you don’t have enough refrigerant, then your air conditioner can’t absorb enough heat to properly cool your air. 
 
Have a professional come and measure your refrigerant levels. If you’re low, that means you most likely have a refrigerant leak somewhere. 
 
WARNING: Don’t have a professional add more refrigerant without finding and repairing the leak FIRST, or you’ll be wasting money. You wouldn’t add more gas to your car without fixing a leak in your tank, would you?

Need help?

If you’re not sure what the issue is and live in that Kansas City area, contact Santa Fe Air Conditioning and Heating for help.