Why Is My Air Conditioner Freezing Up?

Why is AC Freezing Up?

Has your central air conditioner unit unexpectedly turned into an ice maker while blowing warm air out of the air vents? Air conditioner units require regular maintenance and will malfunction if problems arise with the the blower or other systems. Here are several reasons air conditioners freeze up.

Restricted Airflow

A common culprit behind frozen AC units is restricted airflow. When your air conditioner doesn’t receive enough air, the evaporator coil gets too cold and eventually freezes.

The possible cause include:

  • The Furnace Air filter Is Clogged. Regularly replace or clean the air filter in your AC unit.
  • Air Vents Are Blocked – Ensure that all vents and registers are open and unblocked. Closing too many supply registers limits overall performance and can cause freezing.
  • Fan Malfunction – If the fan is not blowing fast enough, it may not be forcing enough air over the evaporator coil.

Low Refrigerant Levels

Low refrigerant levels can make the evaporator coil too cold, causing the ac unit to freeze. This could be caused by a leak or if the refrigerant was charged incorrectly during AC installation. If this appears to be the cause, call an HVAC professional to fix the issue.

Dirty Evaporator Coils

Over time, dirt and debris can accumulate on the evaporator coils, reducing their efficiency and causing them to freeze. Schedule regular AC maintenance and have the coils cleaned by a professional.

Thermostat Problems

If the air conditioner is running more than is necessary or above its capacity, it may cause your air conditioner to freeze. This could be from someone cranking up the AC or an issue with the thermostat.

Drainage Issues

If condensation from the AC unit is backed up outside the condensation pan or floor drain, the backed up water may freeze all the way back to the evaporator coil, blocking additional drainage and worsening the problem. Make sure your drainage system is clear, especially during the hottest parts of the summer.

Preventing Air Conditioner Freezing

As you can see, there are a lot of reasons that an AC unit might freeze. However, the good news is that with regular maintenance and some diligence on the part of the homeowner, you can prevent AC freezing in many cases. Here are some easy steps you can take to prevent your air conditioner from freezing:

  • Have the refrigerant level checked during regular maintenance
  • Change the filter monthly (or as often as your HVAC service provider recommends)
  • Keep supply vents open at all times
  • Have your HVAC technician increase the fan speed if it is too slow
  • Keep the thermostat set to a reasonable level and do not force your AC unit to overwork
  • Inspect your condensate drain and other parts of your HVAC unit regularly to ensure there is not blockage

The Best Way To Prevent AC Units From Freezing

While there are some easy ways to prevent your AC unit from freezing as a homeowner, some of the preventative measures should be completed by a professional HVAC service technician. The best way to avoid any issues that cause an AC unit to freeze is to have regular maintenance performed on your HVAC system. This not only helps to keep the system running properly for many years to come, but a trained technician can also spot potential issues with your heating and cooling system, and get these fixed before they develop into problems. If you are ready to schedule your annual HVAC system maintenance in Kalispell or surrounding Flathead Valley, contact the AC pros at Central Heating Cooling Plumbing and Electrical today.


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