Performed thorough annual maintenance on an AC system today. Started by inspecting and cleaning the evaporator and condenser coils to improve heat transfer efficiency. Checked refrigerant levels and adjusted as necessary using superheat and subcooling measurements to ensure optimal system performance. Lubricated moving parts such as fan motors and bearings to reduce friction and wear. Tested and calibrated thermostat for accuracy and responsiveness. Inspected electrical components for tightness and signs of wear. Cleaned or replaced air filters to maintain airflow and indoor air quality. Completed maintenance checklist to ensure system reliability and efficiency.