How to Properly Troubleshoot Air Flow Problems in HVAC


A huge reason for inflated heating and cooling bills can be attributed to airflow problems within the HVAC system. There are many possible causes, and each result is the same: little or no airflow out of your supply air registers. Determining the cause is relatively easy if you know where to look. Consider some pointers on finding the culprit to low air flow.

Things You'll Need

  • Flashlight
  • Screwdriver
  • Aviation snips
  • Sheet metal patch
  • Check the HVAC filter located on the side of the HVAC unit. This is the number one reason for airflow problems. If it is dirty, there will be significantly reduced airflow, and you will need to replace it.

  • Check the supply air and return air registers. If these are shut or blocked, air can't get in or out of the rooms they feed. Move large furniture away if it is placed in front of the registers. Open registers if they are closed.

  • Check your blower fan for excessive dirt. Running an HVAC unit without a filter can cause the blower fan to get dirty and reduce airflow. Hire an experienced HVAC technician to clean the blower fan if this is the cause.

  • Look at your evaporator coil to see if it is dirty or iced up. You may need to cut an access hole into the supply air plenum to see the coil. You can install a patch afterward. Low refrigerant can cause your coil to ice up when you are running your air conditioner. This will block airflow. A licensed HVAC technician will have to check your refrigerant if this is the cause.

  • Examine all your ductwork to see if it is crushed or pulling apart. Flexible ductwork is especially vulnerable to damage. Replace any damaged ductwork.

Tips & Warnings

  • Change your filter at least every 90 days. This will keep your airflow at adequate levels.
  • If you have pets, check all your return air registers to see if they are clogged by pet hair.
  • If cutting into sheet metal plenum, be careful not to puncture your evaporator coil. Depending on the unit's size, it can be close to the edge of the plenum.

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