Why is My Air Conditioner Blowing Hot Air?

To be honest, even a professional won’t know the answer to this question without an inspection and some troubleshooting.

We’ll go over some of the issues that require professional repair but first let’s make sure the issue isn’t an easy fix that you can handle yourself (and save some money).

AC not blowing cool air? Try our troubleshooting checklist

#1: Check your thermostat settings

What to check: Make sure your fan setting on the thermostat is set to “AUTO”.

Why?: If your fan is set to “ON” instead of “AUTO” it constantly runs regardless of whether the air conditioner is actually cooling the air. The warm air you feel is just the fan circulating lukewarm air when the AC is not running.

Related: Should You Set Your Thermostat’s Fan Setting to “ON” or “AUTO”

#2: Check your air filter

What to check: If your filter is covered in dirt (like the right filter in the picture), replace it right away. 

However, if it’s been a long time since you last replaced the filter and you notice a particularly heavy coat of dirt, there’s a good chance that this is the cause behind your AC blowing warm air.

In this case, you’ll need to hire a technician to inspect the unit and clean your evaporator coil.

Why?: A dirty air filter allows more contaminants to flow through your AC system. Dirt and dust eventually build on your evaporator coil (the coil that cools the air before it is pushed into your home). 

If the coil is caked with dirt it can’t do its job, meaning the air pushed through your vents will be warm instead of cool.

#3: Check the power supply to your outdoor unit

What to check for: When you turn the AC on, do you hear the outdoor unit running? 

If not, you’ll want to locate your breaker (the metal box near your outdoor unit). Flip your AC breaker to the “off” position then back “on” to reset it. 

Note: If your breaker immediately flips back to the “off” position when you try to reset it, do not flip it again! Leave it alone and call a technician immediately. 

Why?: Your air conditioning system has 2 parts: an indoor unit that blows the air through your home and an outdoor unit that cools the air. If your outdoor unit isn’t getting power, your indoor unit may continue to run, blowing your home’s air in circles without actually cooling it off.

If your outdoor unit isn’t getting power, one likely cause is a tripped breaker (sometimes due to a power surge, thunderstorm, etc). Learn more about why your circuit breaker keeps tripping.

#4: Check your outdoor unit for dirt/debris

What to check for: If you notice that your outdoor unit (also called the condenser) is covered in a layer of dirt, turn off your AC then hose it down. This won’t damage the system and will remove most of the dirt.

Also check for weeds, plants, etc. that may be “suffocating” your condenser. Make sure that there is a healthy amount of space (2 to 3 feet) between the condenser and all surrounding objects.

Why?: One of your condenser’s responsibilities is to dump the heat absorbed from inside your home into the outdoor air. 

But if the outside of your condenser is covered in dirt or if debris is blocking its airflow, it can’t release heat very well. That heat then travels through the system and gets pushed back into your home.

AC still blowing warm air?

If your AC is still blowing warm air, there’s probably a bigger underlying problem that needs to be fixed by an air conditioning technician. Some examples include:

  • A leak in your air ducts—Leaky ducts bring hot attic air into your home..
  • Problems with the compressor—Faulty compressors prevent heat from being pushed out of your home, meaning the same warm indoor air is cycled through your AC system instead of cool air.
  • Refrigerant leaks—Refrigerant is what actually cools the air, so if there is a leak, the air pushing through the vents will be warm.
  • Wiring issues—Wires deliver electric power to your AC unit, so if even one wire is frayed or damaged, it may be cutting off power to parts of your system that cool your air.

Let us help you cool off

If you’ve gone through the troubleshooting checklist and your AC is still blowing warm air, we can help (if you live in Hastings, MN or the surrounding area).

Schedule your AC repair with one of our timely, professional technicians. And don’t forget—if we’re late, (even by a minute) it’s free. Try us.

One Hour Air's air conditioning techs serve Hastings, Minnesota and the surrounding areas, including  Apple Valley, Burnsville, Cottage Grove, Eagan, Woodbury, Lakeville, Rosemount and Stillwater.


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