Good example of why filters need to be changed frequently. This system had not had a filter changed in over a year and there was very little airflow over the coil causing the refrigerant temperature to drop below freezing making this huge block of ice on the evaporator coil. It did not help the cooling at all that the condenser coil was caked in dirt and grass too. After thawing out the block of ice and cleaning the outdoor coil out this 23 year old unit runs like new!