Troubleshooting Weak Airflow from Your AC Vents: Causes and Solutions

Imagine you get home on a hot summer day and you’re eager to turn your AC on full blast only to find that the air is barely blowing out of the vents. You’re probably extremely frustrated and wondering what is going on!

If your ac is not blowing hard through the vents you have an airflow problem. You can usually solve this by simply cleaning the air filter or other to allow more air to flow through. If that doesn’t work, however, you may need to enlist the help of a professional to find out which AC component is causing the lack of airflow and help fix it.

In this article, I’ll go over some of the reasons you may be experiencing little to no air coming out of the AC vents in your house. I’ll also walk you through some ways to fix each problem and let you know when it’s best to call a professional.

Why Is My AC Blowing Little to No Air Out through the Vents?

Think of your AC system as one continuous system that moves hot air through various points in the system, to eventually return that air back through the vents in your house. The way it works is it removes the warm air from inside your house, passes it through the evaporator coil which absorbs the heat with the help of liquid refrigerant, and then sends the cooled air over the blower and through the ducts to all of the different vents in your house.

Keeping that air flowing through the system is the most important part of the process. If the airflow gets stopped somewhere along the way, you will ultimately get less air coming out of the vents in your house.

The good news is that low airflow coming out of the vents is generally an easy fix that can be handled by yourself, without the help of a professional.

Let’s take a look at some of the common causes of reduced airflow out of the vents and some possible quick fixes for each issue.

Closed damper

The term “dampers” refers to valves in the ducting systems that control airflow to particular vents in your house. These valves are usually open when your AC system is running.

However, if there is a problem with the ducting system the valve could close, restricting air from flowing through a certain vent. This could cause damage to the system or even, in extreme cases, lead to carbon monoxide poisoning.

If you know where the dampers are, check to make sure they are all open when you are running your AC. Newer AC models even have electric dampers that can be opened and closed using the control panel near the inside AC unit.

If you don’t know where the dampers are located, I’d recommend calling a professional who can help identify the location and determine whether the damper just needs to be opened, or if it is damaged and needs to be replaced.

Leaky Ducts

Ducts are the maze of metal sheet tubbing that connect your AC unit with the vents that carry air into your house. Improperly connected or leaky ducts are a common problem that I see in many homes. Leaks like that will cause the cool air that flows from the AC unit to lose its power by the time it reaches the vent, resulting in little air flowing out of the vent.

This is also a major source of energy loss that could be costing you a lot of extra money on your energy bill, so getting your ducts fixed fast is not only in the best interest of your air conditioner, but your pocket as well. 

Inspecting the ductwork in your house is simple. Climb up in your attic, down in your crawlspace, or wherever your ducts run and look for signs of damage. If you find anything suspicious, you’ll need to seal up the leak yourself or call a professional to help you out.

I’d recommend turning off your AC system before trying to repair any type of disconnect or leak. Then, you can use either aluminum foil tape or duct mastic, which is a substance specifically made to seal ductwork, to get the job done.

Collapsed flex duct 

Ducts come in two different types; the typical ridged metal sheet tubing you probably imagine when you think about ductwork and flex ducts. Flex ducts are just what they sound like – flexible ducts. I prefer quality flex ducts over traditional rigid ducts because they are lightweight and easier to install.

They’re flexible because they use a material called polyethylene. Polyethylene is very strong and is built to withstand high temperatures and humidity. But polyethylene isn’t designed to support heavy loads like those caused by people stepping on them or roughly cleaning them, so sometimes we find collapsed flex ducts. 

A collapsed flex duct will without a doubt restrict the amount of air that is reaching your vents causing it to blow very little air out if any at all. 

You can try to fix a collapsed duct by applying some of the duct mastic that I mentioned above, but if that doesn’t work, you will likely have to replace the bad part of the ductwork. Trying to DIY duct replacement could be difficult and lead to improper installation so I highly recommend hiring a professional to help you out if it comes to that.

Clogged air filter

Air filters are important parts of your HVAC system that remove dust particles from the air before it passes through the evaporator coil in your AC system. A properly functioning air filter cleans the air you breathe while keeping dust and debris from entering your home.

It can also help keep your air conditioner running smoothly by keeping these particles from passing through the system and building up over time causing a blockage in the system.

But when your AC filter gets clogged up, you might notice some airflow problems like low air pressure or no air blowing out of the vents. If you see any of these signs, it may be time to replace your AC filter. And even if you don’t notice any air pressure problems, I recommend checking them at least every 6-12 months.

To change your air filters, first, turn off your air conditioner by hitting the circuit breaker as you should do when working with any type of electrical appliance.

Then, open up the access panel on the indoor unit, take out the old filter and install the new one. Look for instructions on how to properly position the air filter written along the sides of the filter, replace the access panel cover, and then you’re ready to go for another 6-12 months.

Malfunctioning blower

The blower helps pull air from your house and then move the air over the evaporator coils and through the ducts, into the vents in your house. So if your blower is running slow or not running at all, it could reduce the airflow that reaches your vents. 

You’ll probably be able to hear if your blower is malfunctioning since blower problems are typically accompanied by strange sounds, and you’ll definitely be able to feel the loss of airflow through the vents.

If the problem is just caused by dirt and grime buildup on the blower, a good DIY cleaning with a toothbrush or a small sponge could help. But if it is a problem with the blower motor, you might need to replace it altogether. In that case, I’d say you’re better off having an HVAC technician do the job.

Blocked return vents

You wouldn’t believe how many times I’ve seen a simple obstruction in the way of one of the return vents be the cause of the AC not blowing air out the vents hard enough. Well, believe it or not, blocked return vents are one of the most common causes of air conditioner problems.

Furniture placed directly in the path of the air return vents can cause an obstruction. This includes things like wall hangings, curtains, blinds, rugs, and even bedding. 

The less airflow available to flow back into your AC system, the harder the system has to work to cool the air, which, over time, can cause quite a bit of wear and tear on your system and can cause an immediate decrease in the air coming out of the other vents in your house.

As a general rule, I would advise keeping everything at least one foot away from any of the return vents. Anything less than that risks creating an airflow problem in the system.

In addition, you should make sure nothing is blocking the return vents in the attic. That includes insulation, roof shingles, and anything else that could get caught in the return vent.

Frozen evaporator coil

The evaporator coil is the part of the unit that is largely responsible for cooling the air inside your home. If it freezes, it’s another reason airflow won’t be able to make it to your vents.

A frozen evaporator coil could be caused some of the airflow problems that I mentioned above like a dirty air filter, a blocked return vent, or a broken blower. Basically, the loss of airflow restricts the amount of warm air that flows over the coil causing it to get too cold and freeze over.

When that happens, ice and frost from all over the evaporator coil and possibly even on the pipes that go in and out of the AC unit. The ice keeps the evaporator coil from functioning properly so air isn’t moved through the system properly resulting in less air coming through your air vents.

Another thing that can restrict airflow is a dirty air filter. A dirty air filter will restrict airflow because dust and debris build up on the filter itself. As the filter gets

If you’re dealing with a frozen evaporator coil, you should turn off your AC completely and let the coils thaw out. This should fix the problem for the moment and get air flowing back through the system again, but you’ll still want to find the root of what caused the freezing in the first place so that you can repair it before it does any more damage.

Can These Problems Eventually Cause Damage to the AC Unit?

The bottom line is, without airflow, your AC cannot work properly. Remember, your AC system has many different components that need to work together to make sure your home stays cool. And if any of the problems above go untreated for a long period of time, the separate components will start to fail and the entire system will stop working correctly.

Routine maintenance can also help keep your AC functioning properly and save you some of the hassles of having to repair things once they break with my DIY suggestions above.

You should change the filters regularly and ensure that all moving parts of your AC system look and sound good. I actually prefer the air filters that you can see through. They allow for even more airflow and keep your air conditioner running even better.

In addition to DIY inspections, I often recommend having a professional come and check your unit out twice a year, once before it gets too hot in the spring, and again before it gets too cold in the winter.


In conclusion, if you notice that your air conditioner isn’t blowing hard through the vents and you want to fix it, go through the possible causes I’ve listed above as a start to troubleshooting the system.

Ideally, you should try to keep up on prevention and the easy fixes before you experience any bigger problems caused by a continuous lack of airflow which could be as serious as total system failure.

I hope this list helps you get to the root of the issue so you can fix it at the first sign of a problem.