A/C is unpredictable for my ML. Sometimes it's freezing then warm air without touching it! something is stopping the compressor but can't figure out what it is. Sometimes it works most of the days and on some days it'll blow warm air most of the day. First, took it to dealer and they updated the software on AC Control, no difference. The second visit to the dealer, they made sure that it's properly charged with R134. Now 3rd time, at dealer again, they told me he couldn't duplicate the problem... I just can't believe that they can't find the problem. Any ideas? please help!