The answer to 'evaporator coil freezing up' is that it is a common issue caused by a variety of factors, including low refrigerant levels, airflow restrictions, and compressor problems. Symptoms include the coil becoming completely covered in ice, reduced airflow from the vents, and the system not cooling effectively.
In many cases, a frozen evaporator coil is caused by a lack of airflow over the coil. This can be due to a dirty air filter, a blocked return vent, or a problem with the blower fan. Low refrigerant levels can also cause the coil to freeze up, as can issues with the compressor. Resolving the underlying cause is key to preventing the coil from freezing again.