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 ML320 AC System Leaks/Bad Temperature Sensors May Cause Poor Cooling
Mercedes-Benz ML320 Problem
Average Mileage: 122,554 mi (69,324 mi - 150,000 mi)
Visitor, 1999 Mercedes-Benz ML320
My AC stop working. It is blowing air but it is not cooling. I replaced blown fuse still is not working.
A/c needs to be recharged with stop leak refrigerant and new freon every year.
Haven't got it fixed. Was quoted replace evaporator -- over 20 hours labor plus part! Around $2000
we had our mechanic refill freeion 3x for the last 6 months. it doesnt work again.
Visitor, 2001 Mercedes-Benz ML320, 69,324 mi
Sometimes when you first get in and start up the car it can take up to a mile of driving to get the airconditioner to the point of blowing cold instead of cool air,