Investigating And Troubleshooting An AC Low Air Flow Issue

25 August 2016
 Categories: , Articles


If you have been experiencing the extremely hot temperatures that have plagued the United States over the last year, then you may be putting your central air conditioner through its paces. If air flow coming through your vents suddenly drops, then you may be nervous that your overworked system is ready to completely break down or fail. This is probably not the case, and there are a few things you can investigate to fix the issue. Looking at your filters and your ducts is one important thing to do. 

Change All Air Filters

Plenum Filters

Your air conditioner will have an air filter that helps to remove dirt and allergens before the air is moved into your home. Most people know that they need to change filters, and it is wise to do this at least every three months. However, extensive use of your cooling system may mean that a replacement is needed much more quickly. Inspect your air conditioner about every four weeks. If the filter appears gray, then it should be replaced immediately.

Some central AC units will have a single filter that sits in the plenum. The plenum is the square box that sits between the AC unit and the ductwork. You likely have a filter in the plenum, but you also may have one or several filters located elsewhere. If these filters have not been changed at the same time as the plenum one, then this may be the reason for the sudden air flow issue.

Air Intake Filters

You may have a filter attached to the air intake that pulls fresh air into the AC unit. The air intake is often called the air handler, and it can be found in either your attic or along a duct that is attached to the outside of your home. Follow your ductwork, look for the air handler, and find the attached filter. The air handler or air intake will pull in a great deal of dirt and debris, and this is why thick, pleated filters are typically attached to air handler units. Make sure to pull the filter out of the intake to see how thick the filter is. The filter can be up to five inches thick, so take a measurement before purchasing a new one. 

Your air intake may also have a device called an electrostatic precipitator or an electrostatic air cleaner attached to it. These devices use an electrostatic charge to collect dust particles, much like an air purifier. If you notice a large square device attached to the air handler or intake system, then this is the electrostatic cleaner. The cleaner may have a grate on the front and a filter behind it. Clean the grate and also replace the filter to help encourage good air flow.

Look For Duct Leaks

The ducts in your home can form holes that allow cool air to escape before it reaches the interior of your house. Small holes are common and can cause a slight drop in air flow. Larger holes will create a large drop in airflow though, and this can be the cause of your AC difficulty. To see if a hole or opening is present, visually inspect the ducts leading to and from your AC system. There are several different types of holes you may see. One of the seams may have opened, and you might see a large gap between two sections of the ducts. If you notice this, then purchase some short self-tapping sheet metal screws at your local home store. Push the two sides of the ductwork together, and use a drill to add four or five of the screws to the seam to connect the two ducts together.

If you notice a number of small or medium sized holes around the ducts, then purchase some mastic sealant or some metal-backed tape to make a repair. Place the tape or sealant over the opening. If you decide to use the mastic to cover the hole, turn off your AC unit while making the repair and allow the material to cure before starting up your cooling system again. 

If you have more complicated issues or cannot find the source of the problem, contact professionals in your area, such as those at Winters Heating Cooling.