How to check AC coils?

How to check AC coils involves inspecting both indoor evaporator coil and outdoor condenser coil for dirt, damage, ice, and airflow blockage, with power off for safety. To check evaporator coil indoors: first turn off power to furnace and AC at breaker and thermostat, second locate air handler or furnace, remove access panel to reveal A coil, third visually inspect coil fins and tubes for dust buildup, mold, bent fins, ice formation, or oil residue indicating leak, use flashlight, fourth check condensate drain pan and line for clog. To check condenser coil outdoors: first turn off power to outdoor unit, remove leaves and debris around unit, second visually inspect outer coil fins for dirt, cottonwood, bent fins, or damage, third look through fins to see if light passes indicating cleanliness. You can also check coils performance by feeling airflow and temperature difference. If coils dirty, clean gently with soft brush and coil cleaner spray, do not use high pressure water that bends fins. For thorough check, technician may measure temperature split and pressures. Regularly checking coils every few months helps maintain efficiency.