An evaporator coil is the indoor coil of a central air conditioner or heat pump, usually an A-shaped coil above the furnace or inside the air handler. Cold refrigerant in its tubes absorbs heat from household air as the blower pushes air across its fins, and moisture condensing on the coil drips into a drain pan below.
Why it matters to you
A dirty or iced evaporator coil cuts airflow and cooling capacity, and its drain pan is where many indoor condensate leaks start.
Practical guidance
Change the air filter on schedule, since a clogged filter is a leading cause of a frozen coil. If you see ice on the coil or the refrigerant lines, switch cooling off and run the fan to thaw it, then have airflow and refrigerant charge checked.