Maintenance and service must be performed by a qualified installer or service agency. At the beginning of each cooling season, the system should be checked as follows:
NOTE ‐ If insufficient heating or cooling occurs, the unit should be gauged and refrigerant charge should be checked.
It may be necessary to flush the outdoor coil more frequently if it is exposed to substances which are corrosive or which block airflow across the coil (e.g., pet urine, cottonwood seeds, fertilizers, fluids that may contain high levels of corrosive chemicals such as salts)
Source: MaintainX (Community Member)