Why AC Airflow Is So Weak? How to Improve It?

Your air conditioner won’t be able to effectively cool the house if the airflow is weak. There are a few things that can cause such an issue.

Weak AC airflow can be caused by dirty air filters, blocked registers, leaky ducts, a frozen coil, and a faulty blower. Changing the filter and clearing the area around the vents usually helps; you might also have to clean and seal the ducts and check the evaporator coil and blower.

Why AC Airflow Is So Weak? How to Improve It?

There are quite a few reasons why your AC airflow can be weak. The good news is that the majority of them are a relatively easy fix.

  • Dirty air filters – for max efficiency, you might want to consider replacing your AC filters every 45 days or so. However, if you don’t have any pets and allergies, then once every 3 months should be enough
  • Blocked registers and vents – to promote free airflow, make sure to leave at least 18 inches between any objects in your room and the air vents
  • Blocked ducts – you might want to have the ducts professionally cleaned every 2-3 years.
  • Leaky ducts – you won’t have proper airflow in the system if a part of the air can’t make it to the registers. Inspect the ductwork and seal off any gaps.
  • A malfunctioning blower – the fan is the element that is responsible for moving the conditioned air through the ducts. If grime has accumulated around it or if the fan motor is failing, you will have issues with the airflow.
  • A frozen evaporator coil – the coil can freeze if there is insufficient airflow, but it can also lead to problems with the airflow. Ice will form over the coil, in case there is a refrigerant leak or if the coil is dirty. 

What Causes Weak AC Air Flow?

  • A dirty air filter
  • Blocked or leaky ducts
  • Blower malfunctions
  • A frozen evaporator coil
  • Blocked or closed off registers

Read: Why HVAC Damper Keeps Getting Stuck Closed?

Uneven Air Flow from AC

If you’re experiencing low airflow only in a certain part of your house, then one of the following issues might be to blame:

  • Leaky ducts – if there are leaks in your ductwork, some rooms won’t be getting as much air pushed through as others
  • An incorrectly sized unit – an air conditioner that is too small for your house would be able to effectively cool the rooms that are closer to the unit, but the spaces that are farthest are not going to receive enough airflow
  • Improperly installed ducts – the ducts that are bent or crushed won’t be able to let enough air through
  • Not enough return vents – if your house doesn’t have enough return vents, then the HVAC system won’t be able to pull enough air back. This will result in inconsistent airflow

Why Is My AC Barely Blowing Air?

If you’re sure that your air filters are clean, that the ducts are in great shape, and that the evaporator coil is not frozen, then issues with the blower might be the reason why there is barely any air coming from the vents.

The blower won’t be able to function properly if it has a stuck wheel, a loose belt, a dead motor, or a fan that is clogged with dirt

Read: How To Tell If HVAC Zone Damper Is Normally Closed Or Normally Open? 

Why Is My Home AC Not Blowing Hard?

If a recently installed air conditioner is not able to blow hard, then the chances are high that the system is simply too small for your house

Buying an AC of the right size is vitally important. If you live in zone 2, for example, then the cooling capacity of your air conditioner should be 35-40 BTUs per square foot.

Why Is My AC Not Working as Well as It Used to?

Make sure that the thermostat settings are correct, replace the filter, and schedule a professional AC cleaning. 

Have a Question? Ask HVAC Technician

Click here to use the chatbox to speak with one of our technicians.
No in-home service calls. No appointments.

If it has been over 2-3 years since you installed the air conditioner, then it might have stopped working as effectively simply because plenty of dirt has accumulated in the unit during this time.

If your air-con is over 10 years of age, then, in the majority of cases, general wear and tear are to blame

What to Do If No Air Is Coming Out of Vents in One Room?

  • Some vents have a damper inside; make sure that it is open
  • If the room is the farthest from the AC unit, then your system is undersized for your house
  • The duct through which air travels to this room might be disconnected or damaged

How to Increase Airflow in Ductwork?

Changing the air filters and cleaning the ducts is the best way to increase airflow. Also, do check the ducts for any leaks from time to time.

If you’re considering investing in additional equipment, then you might want to go for an inline booster fan or air dampers. The latter won’t really increase airflow, but they’ll help regulate it more efficiently. 

Read: Why HVAC Zone Damper Actuator Making A Clicking Noise? How To Troubleshoot?

How Can I Help My AC Circulate?

Switching the fan mode on will help your air conditioner circulate the air more effectively. 

If you have ceiling fans, you might want to strategically use those as well – simply turn them on together with the air-con to help the cooling system distribute the conditioned air more evenly.

Does Putting a Fan in Front of AC Help?

Placing a fan in front of your window AC or near central air vents will help the unit circulate the cool air over a wider area and this, in its turn, will help you reduce your energy bill.

If you are using a ceiling fan, make sure that its blades are spinning counterclockwise in the summer.

Read: Should An HVAC Zone Damper Bleed Air?

How Much Air Should Be Coming Out of Vents?

It might be challenging for a regular homeowner to figure out exactly how much air should be coming out of the vents. But there are two rules that you can use as a guideline:

  • You should be feeling air coming out of the vents
  • The air coming out of the vents should be roughly equal throughout the whole house

How Cold Should the Air Be Blowing Out of the Vents?

The air coming out of the vents should be 14-20 degrees colder than the air flowing into the system.

How Many BTU Do I Need for a 12×12 Room?

Properly sizing your cooling system is the first step in making sure that your house is not going to experience any airflow-related problems.

Typically, a 12×12 room is going to need 5,000 BTU of cooling capacity

Read: How Reliable Multi-Zone HVAC Systems Are?

How Do You Balance AC Air Flow?

To make sure that the airflow is consistent throughout your whole house, you should:

  • Keep the vents and rooms open
  • Improve the insulation in your house
  • Fix the ducts whenever there is such a need
  • Regularly replace the air filter
  • Consider installing a zoning system

How Do I Increase the Air Flow in My AC Upstairs?

You can choose to increase the size of the vents and the ducts on the second floor. If that is not possible, then increasing the number of vents might be a better solution.

Getting a zoned HVAC system will help you avoid such problems, as you’d be able to set the thermostats to different temperatures on different floors.