AC system leaks and/or a faulty evaporator temperature sensor can cause poor AC cooling. The failed sensor can prevent the AC compressor from coming on. Leaks cause a low refrigerant level, which reduces the ability to cool.
Car Problem Reports
Mercedes-Benz ML350 AC System Leaks/Bad Temperature Sensors May Cause Poor Cooling
Mercedes-Benz ML350 Problem
Average Mileage: 88,212 mi (80,000 mi - 96,425 mi)