Your air-conditioner’s job is to regulate indoor temperatures. However, there are times when the process can go wrong, making the A/C freeze. There are several potential causes, which can be related to airflow or refrigerant issues. These are some of the most common causes of A/C freezing:

  • Dirty coils – An A/C normally pulls water out of the air to dehumidify it. This is how condensation builds up on the coils. Although this is not usually a problem, dirt inside can keep the coils from absorbing moisture. Eventually, the water can build up and freeze over the coil. Regular inspections by HVAC professionals can prevent the buildup of dirt.
  • Drainage problems – Normally, water from the evaporator coils drip into a drainage pan and out a drain. If the drain is blocked, the water can freeze and back up to the evaporator coil. As the water freezes, the drain becomes further blocked, which can escalate the problem.




  • Low refrigerant levels – If your A/C lacks refrigerant, the pressure difference in the system causes moisture to condense on the evaporator coils. Condensation normally forms outside the lines. However, the lack of refrigerant brings the temperature to lower than normal levels. Eventually, the temperature will drop, freezing over the coils.
  • Poor airflow – A dirty air filter can affect the flow of air to the A/C. The airflow brings in heat from inside so that the system can cool the room. If there isn’t enough air flowing through the system, heat exchange can’t take place. The coils are designed to have humid air pass over them to prevent freezing. Without proper airflow, however, the moisture will eventually freeze.
  • Damaged blower fan – An air-conditioning unit has a fan as part of the system to suck hot air away and replace it with cold air. If the fan doesn’t work properly, the airflow becomes disrupted. Cold air can’t flow properly, causing temperatures inside the system to drop. Eventually, condensation on the coils can freeze. The freezing can spread to the refrigerant line and affect the condenser unit outside.
  • Thermostat issues – A faulty thermostat can cause problems during cold nights. In these cases, the A/C is left running, even when it shouldn’t be. Not only can this freeze the system over, it wastes energy and money. Have the thermostat checked regularly to ensure that everything is running smoothly.


Your air-conditioning requires regular maintenance to run smoothly. Contact a professional HVAC service to ensure that everything is operating as it should, preventing costly repairs in the future.


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At Dr. Duct, we are committed to providing air duct cleaning to for clean, healthy airflow. Whether commercial or residential, we provide quality service and personalized care to all our clients. Call us at (613) 845-0707 for a free estimate.