Conducted comprehensive maintenance on Trane XL18i air conditioner, model 4TTX8060A1000AA. Cleaned condenser coils using Nu-Calgon Evap Pow'r-C and 1800 PSI pressure washer. Checked refrigerant charge with Testo 557s digital manifold, adjusted to manufacturer specifications. Replaced clogged 20x25x1 MERV 11 air filter. Inspected and tightened electrical connections, measuring voltage drop across contactor. Lubricated condenser fan motor bearings with SAE 20 non-detergent oil. Cleaned condensate drain line with CO2 blast cartridge. Calibrated Trane ComfortLink II thermostat and verified system performance through all operating stages.