• Howard Gallagher

Why Is My Air Conditioner Frozen?

One of the most unique sights to see is during a hot day and you notice your air conditioning unit is frozen. What you are witnessing is The Joule-Thomson Effect .It is a simple phenomenon that happens with gases. As gas expands , its pressure and temperature decrease. Vice versa when gas compresses then its temperature increases. The evaporator coil in your system is the component of the system that is responsible for the expansion of the air flowing through the system. If there is any malfunction with the flow of heat in the unit, then the unit will freeze over.

Causes Of A Frozen Air Conditioner

There are several reasons why your ac unit is frozen. One factor could be differences in temperature between the unit and its surroundings. Spring weather has cool mornings and warm days. So in event your ac unit is running all day it may freeze due to not being able to function in temperatures below 60 F. If you notice temperatures may dip in morning time then turn off your unit until it is warm enough. Insufficient air flow is another reason why your air conditioner may freeze up. Humidity collects on evaporator coils. If there is no air flow then moisture will start to freeze up and reduce the efficiency of your unit. A malfunction in the air filter, blower fan and evaporator coils can cause this issue. Lastly if your unit’s refrigerant levels are low or is leaking then your unit can freeze over.

What To Do When Your Air Conditioner Is Frozen


The first thing you want to do if you notice your unit is frozen is to defrost your unit. Start by turning off the thermostat. Next turn the fan setting on. Since you turned the thermostat off refrigerant is no longer being sent to the compressor. Now warm air from the fan is being blown into the unit’s frozen coils. Much like defrosting your refrigerator it is not immediate. It can take anywhere from 1 hour to 24 hours. Keep in mind as the ice melts put towels near the drain pan and the condensate drain line to prevent water damage. Finally check your air filter. If it is dirty that may be your culprit. Otherwise it may be an issue with one of the major HVAC components. You would need to contact a licensed and bonded contractor to look at the issue.

Frozen Air Conditioner Preventative Maintenance


Proper Maintenance can always improve the longevity of your unit. Clean or replace your air filter as a part of seasonal maintenance. A clogged or dirty air filter can restrict air flow in the home. Clean evaporator coils on a regular basis. Dirty evaporator coils can be the key area that causes a frozen unit. Make sure your refrigerant levels are checked and maintained.