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.Google+
Car Problem Reports
Mercedes-Benz ML500 AC System Leaks/Bad Temperature Sensors May Cause Poor Cooling
Mercedes-Benz ML500 Problem
Visitor, 2005 Mercedes-Benz ML500
the AC blows out warm air..sometimes works though...when it 1st started happening, it seemed like if I rolled the window down the AC would start working..
Visitor, 2002 Mercedes-Benz ML500, 83,000 mi
When i am turning on AC in my car radiator fan is working on high speed, and i have no cold air. I changed auxiliary water pump & i still have the same problem.I have full freon in system. Thank you.