Evaporator Coil

The evaporator coil sits inside your indoor air handler and is where refrigerant absorbs heat from the room air. As warm air passes over the coil, the refrigerant inside evaporates, pulling heat out of the air in the process — which is how the room gets cooler. If the coil freezes up, it's usually a sign of restricted airflow (often a dirty filter) or low refrigerant. A frozen coil won't cool effectively and can damage the compressor if left unchecked.