What can cause ice buildup on an A/C unit?

Ice buildup on an A/C unit is primarily caused by low refrigerant levels or poor airflow. When the refrigerant levels are low, the pressure in the system drops, leading to reduced cooling ability and causing the evaporator coil to become too cold. If the coil temperature drops significantly, moisture in the air can freeze on the coil, resulting in ice formation.

Similarly, poor airflow can also lead to ice buildup. This can occur if the air filters are dirty, leading to insufficient airflow across the evaporator coil. When the coil does not receive enough warm air to transfer heat, it can again become too cold, resulting in ice accumulation.

In contrast, excessive refrigerant levels typically do not cause ice to form; rather, they can lead to other issues within the system. High ambient temperatures generally do not cause ice buildup, as they would typically promote normal operation of the A/C unit. Faulty thermostat settings might lead to improper cycling of the unit but are not directly responsible for ice formation on the evaporator coil.