Why Does an Air Conditioner Freeze Over?

In Heating & Cooling 101, Uncategorized by YounitsLeave a Comment

Freezing condensers are a common problem and often result in a service call.  There are only a few reasons why this occurs and only a licensed professional can diagnose which problem you are having.  Below are some of the more typical possibilities for why your condenser is icing over.

  • Coil is not matched properly.  All condensing units have an evaporator coil, which sits on either your furnace or air handler.  If the coil is too big or too small for the capacity of the condenser, it will not work properly over time and can eventually lead to your AC unit freezing over.
  • Outdoor temperature is too low.  Air conditioners do not function well when the outdoor temperature is at 60° F or below.  This can cause freezing issues.  Be mindful of dipping overnight temperatures and consider setting your system so it doesn’t turn on at night if the temperature will be too low.
  • Low refrigerant.  All air conditioners need refrigerant to operate.  If your ac is icing over, you may want to have a licensed professional check the refrigerant for leaks, usually in the refrigerant line.  Do not attempt to check or replace refrigerant yourself.
  • Blocked airflow.  This is a very common cause for condensers freezing up.  Usually, poor airflow is the result of a dirty filter, especially if the unit has been running constantly.  This is a good 1st item to check if your unit is having freezing issues.  If the filter is dirty, change it and see if the issue improves.
  • Mechanical issues.  If none of the other items is the problem,  you may have a mechanical issue to be checked by a technician.

Preventative measures are a good way to keep your air conditioning system from freezing over.  Pre-cooling season, have routine maintenance done on the unit.  This will eliminate most of the issues that might cause freezing if they are caught ahead of time.  In addition, check your filter once a month during the prime cooling season to make sure the unit is getting proper air flow.

Have questions about air conditioners or coils?  Representatives from are available from 9 a.m. to 5 p.m. CST M-F at 800-880-0199 or feel free to e-mail us anytime at

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