Diagnosed and repaired failed capacitor on Trane XR13 system. Unit wasn't starting properly and making buzzing noise on startup attempts. Replaced with correct 45/5 MFD dual capacitor and tested operation. Also discovered minor refrigerant leak at Schrader valve - replaced valve core and pressure tested system. Cooling restored to 100% functionality with appropriate temperature differential across coil. Left homeowner with information about our maintenance program to prevent future issues.