Air conditioner coils freezing

If your air conditioner coils are freezing, the problem usually starts with restricted airflow. A dirty or damaged air filter is the most common cause because it limits air moving across the evaporator coil, letting the coil get cold enough for moisture to freeze. If the AC coils are frozen in only one section, a sealed system refrigerant leak may be involved, which requires a licensed technician. A dirty evaporator coil can also cause evaporator coil freezing, especially when combined with a clogged air filter or dirty blower wheel. On many window units, a failed dual shaft fan motor or fan motor can stop the fan blade or blower wheel from moving enough air, leading to a window air conditioner freezing up and possible compressor overheating. Start by checking and cleaning the air filter, then inspect the evaporator coil and airflow components. If a part needs replacement, enter your air conditioner model number on RepairClinic.com to find the exact air filter, fan motor, dual shaft fan motor, blower wheel, or related replacement part made for your specific unit.

01 - Dirty or Damaged Air Filter

If the air filter becomes clogged with dirt, it restricts airflow over the evaporator coils. If the airflow is reduced, the evaporator coils get too cold, which then causes the humidity in the room to condense on the coils and freeze. As frost accumulates on the coils, the frost restricts the airflow even more. Eventually, the entire evaporator coil assembly will frost over, causing the airflow to be completely restricted. Most air filters used in stand-alone air conditioners can be cleaned with soap and water. Only filters that are extremely clogged with debris or damaged will need to be replaced.

02 - Sealed System Leak

If the air conditioner coils are freezing in only one area, there may be a sealed system (or refrigerant) leak. This is normally a very expensive repair. Repairs to the sealed system must only be performed by a licensed technician.

03 - Dirty Evaporator Coil

Proper air flow is critical for the air conditioner to work properly. The evaporator needs sufficient air flow to keep the condensing water from freezing. If the evaporator coil, air filter or blower wheel gets clogged, air flow will be reduced and ice can start forming on the evaporator coils, eventually freezing them up. It is recommended to replace the air filter routinely. Refer to owner's manual for air filter replacement frequency recommendations and for evaporator coil cleaning instructions.

Highly Likely

04 - Air Conditioner Fan Motor

An air conditioner fan motor is the component that spins the fan blade or blower wheel to circulate the air. If one of the fan motors is burned out, the air won't be circulated properly which can cause the coils to freeze. You can use a multimeter to determine if power is reaching the fan motor. If power is reaching the motor, but it doesn't run, the component will need to be replaced.

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05 - Air Conditioner Blower Motor

Since the air conditioner's blower motor is the component that circulates the air through unit to cool it, a defective blower motor could result in the coils icing up. You can use a multimeter to test the blower motor for electrical continuity, a continuous electrical path present in the motor, as well as determine if power is reaching the motor. You can also try turning the blower wheel by hand. If the wheel does not turn freely, it's likely the motor bearings have seized and the blower motor will need to be replaced.

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06 - Air Conditioner Air Filter

If the air filter is clogged, air cannot flow properly through the air conditioner. This greatly reduces the cooling capacity of the air conditioner. In addition, if the air filter is clogged, the evaporator coils will frost over. Most air filters used in stand-alone air conditioners can be cleaned with soap and water. Only filters that are extremely clogged with debris or damaged will need to be replaced.

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07 - Air Conditioner Dual Shaft Fan Motor

An air conditioner dual shaft fan motor is the component that spins the fan blade and blower wheel to both draw air into the unit and force it through the front vent and out the rear condenser coil. If the fan motor is burned out, the air won't be circulated which can cause the coils to freeze and the condenser and compressor to overheat. You can use a multimeter to determine if power is reaching the fan motor. If power is reaching the motor, but it doesn't run, the component will need to be replaced.

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