Performed comprehensive preventive maintenance on residential split air conditioning system. Followed lockout/tagout procedures, disconnected power supply. Cleaned indoor and outdoor coil surfaces using approved foaming coil cleaner. Flushed condensate drain lines with nitrogen purge. Lubricated fan motors, checked belt tension. Inspected electrical connections, tested safety controls. Measured refrigerant charge, validated proper operating pressures and temperatures. Restored power, verified system operation within designed parameters. Optimized for peak efficiency and extended service life.