AC not blowing cold air? Here’s how to fix it

Don’t sweat. In this guide, we’ll help you troubleshoot an AC system that’s blowing warm air so you can get back to feeling great.

Don’t sweat. In this guide, we’ll help you troubleshoot an AC system that’s blowing warm air so you can get back to feeling great.

It’s a tale as old as HVAC systems: A summer heat wave hits and you just want to retreat into your home, where the indoor air is nice and cool. But what if your AC is not blowing cold air?  

An air conditioning unit blowing warm air isn’t just uncomfortable, it can lead to muggy rooms, poor air quality, and ​​high humidity in the house

But why is your AC blowing warm air? Well, no matter the cause, we’ve got some fail-safe solutions.

We’re Sealed, and solving HVAC problems is kinda our thing. And, depending on where you live, you could get a super-efficient electric heat pump HVAC system replacement—along with any eligible rebates—at no upfront cost. Tap here to see if your home qualifies.

By the end of this article, you’ll know how to get your air conditioning system back into shape—so your home stays cool and comfy all summer long.

Here’s what we’ll cover:

Reasons your AC is not blowing cold air

Nothing is fun about being trapped in a hot, stuffy house with no signs of relief. If you’re sweltering in the heat thinking, why is my air conditioner not blowing cold air? We hear you! 

Let’s dig into the nine most common reasons for an AC blowing warm air. 

Reason 1: Your thermostat settings are wrong 

Sometimes the reason why your central AC is not blowing cold air starts and stops at your thermostat. Sound too simple? Maybe, but it doesn’t hurt to check these two things:

  1. See if your system is set to ON (fan mode). If it is, this might be your problem. Try switching the setting to AUTO. This easy fix will ensure your AC fan is only blowing cooled air into your home.
  2. Some thermostats require batteries to work properly, so it might be time to replace them. Easy-peasy.

(Read What’s so smart about smart thermostats? to learn how smart thermostats can help cut energy waste and effortlessly keep your home at your desired temperature setting.)

Did you know? More than half of energy use in homes is for heating and air conditioning.

U.S. Energy Information Administration

Reason 2: You have a refrigerant leak

Your AC will not blow cold air if you have low refrigerant levels. 

HVAC systems give off a distinct hissing noise from the refrigerant lines when there’s a leak, so keep your ears perked. (You can also look for ice buildup if you have frozen evaporator coils, but they won’t be easy to spot if your AC is blowing warm air.) 

IMPORTANT: If you suspect you have a leak, turn your AC off immediately. Refrigerant leaks can be toxic and make people sick, so you’ll want to call in an HVAC professional ASAP!

ac fan always running

Reason 3: Your coils need to be cleaned

Most AC units have two sets of coils: evaporator coils and condenser coils. Over time, both types can get dirty or grow mold. To keep your AC from blowing warm air, these coils should be cleaned well at least once a year.

In fact, calling in a reputable HVAC company to tune-up and clean your entire system will increase energy efficiency and decrease the chances of a major AC repair due to lack of maintenance. Plus, leaving the dirty coils, clogged drains and drain pipes to the pros to scrub will free up your Saturday so you can binge-watch your favorite series in a nice, cool home.

But if you feel like going the DIY route, tap here to learn the steps for cleaning AC coils.

Reason 4. Your air filters need to be replaced

If your air conditioner is not blowing cold air but is running, try changing the filter. Air filters have a pretty dirty job. They trap dirt, dust, and other airborne particles before they reach your home’s internal airflow. 

Most HVAC companies recommend changing dirty filters every 90 days, possibly more often if any of the following factors are overworking your filters: 

  • Your home’s size (larger homes might need more frequent filter swaps)
  • You have indoor pets
  • If anyone in the home smokes or vapes
  • If people in your home have allergies

Reason 5: Your compressor malfunctioned 

The compressor is like the heart of your AC unit—it controls all the other parts of your air conditioner.

In addition to your AC not blowing cold air, signs of a broken compressor are shaky, noisy units or moisture around your AC system.

Reason 6: Your outdoor AC unit is clogged

Branches, leaves, and shrubs—oh my! Your outdoor AC unit weathers every storm and gust of wind, so there’s a chance the elements have caused clogs and buildup. 

While a few twigs are usually harmless, debris on or around outdoor AC units can overwork and overheat your system, which can cause it to—you guessed it: blow warm air.

The good news is, with regular maintenance, some types of AC units can last up to 20 years, especially if your home has sufficient insulation and air sealing.

With regular maintenance, some types of AC units can last up to 20 years, especially if your home has sufficient insulation and air sealing.

air sealing ductwork

Reason 7: You’ve got a duct leak 

Air goes on an epic journey through a series of ducts before finally reaching the rooms in your house. 

Over time air ducts can slightly separate from your air vents, creating gaps and cracks that let all that cool air escape into your attic or other obscure places. 

And if the cool air is escaping, that means your ducts are delivering warm air into your home, making it difficult to keep your home cool and comfortable.

Learn how proper air sealing and insulation (including sealing up air leaks caused by aging ductwork) help bring total comfort to your home.

According to Energy Star, 20–40% of conditioned air that moves through ductwork is lost due to duct leaks. That’s a lot of waste.

Reason 8: You’ve got a tripped circuit breaker

Imagine an AC fix as easy as flipping a switch. Well, if your AC stopped blowing cold air because of a tripped circuit breaker, you’re in luck. 

AC units usually use two circuit breakers, one inside and one outside. If your outside breaker is tripped, you’ll notice the air conditioner running but blowing air that’s warm instead of cool.

No problem. A quick breaker reset and you’ll be good to go. 

Reason 9: AC unit needs to be replaced

Now we’ve reached the biggest reason of them all: You’re due for an AC unit upgrade. 

If your AC unit is still acting up after you’ve tried everything (and have called in the pros), it may be on its last leg. Tap here to discover when it’s time to upgrade your HVAC system.

Think it might be time to replace your HVAC system? Typically, you’ll need $5,000–15,000 upfront and out-of-pocket for your AC (not including ductwork repair or a new heating system), but there are other options. 

Call Sealed—our expert team is here to help. If your home is eligible, you can get an energy-efficient heat pump heating and cooling system to replace your aging AC at no upfront cost—installed by a vetted local contractor you can trust. Learn more.

illustration of a woman fanning herself on the floor of a hot, humid living room

What to do if your AC is still blowing warm air 

So now that you’re done troubleshooting your AC unit’s warm air problem, it’s time to decide whether to outsource your AC repair or try some fail-safe DIY fixes on your own. 

Sometimes the best approach is a professional one. Central air conditioner repair costs anywhere from the lower hundreds to over $1000.

But if you’re looking at an AC replacement, you’ll want to go with a super-efficient, long-lasting solution: a heat pump.

Don’t let the name fool you. Heat pumps get their name because they remove indoor heat and transfer it outside. They cool your home in the summer months, and then, they heat your home in winter by reversing the process. 

Heat pumps (also known as mini-split AC or ductless heat pumps) run on clean, non-combustible energy that can drastically reduce your carbon footprint. Plus, heat pumps dehumidify and purify your home’s air while using as little as ⅓ the energy of traditional HVAC systems—it’s why we’ve dubbed them the Tesla of HVAC.

Heat pumps are the most efficient, best alternative to a traditional HVAC system. (Curious? Check out our complete heat pump guide or watch the video below to learn why heat pumps are a life upgrade.)

Why sealing and insulating your home can help keep your air conditioner cool 

Two powerful upgrades work together to keep your home feeling great year round while also cutting energy waste: air sealing and insulation.

professional attic insulation upgrade

But how do air sealing and insulation work to keep your house cool, exactly?

For starters, air sealing and insulation reduce your AC’s workload, increasing its lifespan—and your home stays cooler on the hottest of days (with less energy used!).

Air sealing seals every nook and cranny in your house to keep outside air out, and inside air clean and comfortable. A properly sealed home improves your air quality and lowers humidity levels. Learn more about air sealing in our complete guide here.

High-performance insulation protects your home against uneven temperatures, no matter the weather. Make sure your insulation is up to the job with our total insulation guide.

Learn how to make your house more comfortable and efficient all year long.

49% of homeowners don’t know that most home energy waste is related to heating and air conditioning. (And air sealing and insulation can help stop it!)

 —Sealed Wakefield Research US Homeowner Survey 2021

Frequently asked questions 

Check out the list of FAQs below and use the links to jump ahead if needed.

Don’t see your question here? Talk to us. We’re here to help!

Why is my AC running but not cooling?

If your AC unit stopped blowing cold air, odds are it’s summertime. That means weeks of unbearable heat if you don’t troubleshoot the issue. So what’s causing it?

Here are 9 common causes of an air conditioner that’s running but not cooling:

Is all the summer heat in your house traveling upstairs? Learn how to get rid of uneven temperatures in your house. 

How do I fix my AC not getting cold?

Once you’ve figured out the root cause of your AC not blowing cold air, you may be able to fix it on your own. Resetting a thermostat or changing an air filter doesn’t take a brain surgeon. But more complicated issues like refrigerant leaks or a bad ductwork require a professional. 

Want to learn more about getting a modern HVAC upgrade at no upfront cost? We can help.

How do you know your AC has a cooling problem?

Troubleshooting an AC cooling problem can be tough. Here are a few fail-safe ways to get started: 

  • Set your thermostat to AUTO
  • Replace dirty air filters
  • Look and listen: for hissing or rattling sounds and extra moisture around your unit
  • Call Sealed. We’ll help you find a trusted HVAC pro.

How do I control the air in my AC?

Change your thermostat settings to AUTO to stay in control of the air in your AC and reduce energy waste at home.

Not sure if your house and AC are actually wasting energy? Learn the signs of energy wastage.

How do I get a new AC system at no upfront cost?

Don’t suffer through another hot summer with your old, worn out air conditioner. Your house may be eligible for an energy-efficient HVAC upgrade plan from our comfort and climate control experts, at no (or very little) upfront cost. 

Our customized plans are tailored just for your home’s needs. Plus, our whole-house approach has been proven to cut a home’s energy use by up to 50%

We take care of everything: troubleshooting, hiring certified home performance contractors, and (most importantly) making sure the work gets done right.

Discover for yourself how amazing your house could feel after working with Sealed. 

It’s as simple as answering a 2-minute questionnaire to see if your home qualifies.

We take care of everything: troubleshooting, hiring certified home performance contractors, and (most importantly) making sure the work gets done right.

August 5, 2022