I too am having the same or similar problems in my 86 190 2.3. Cool mornings and cool evenings are no probelms, blows cold. Hot days(90+) and it will blow semi-cool, and then sometimes even warm air. This car was converted from R12 to 134a recently. During the day when it is blowing warm, I have checked, and the compressor is running. Not really sure what to check next. I would be interested in hearing more about other people with this problem. Thanks...BTW this is a GREAT forum, especially for me, a first time Mercedes owner. Thanks to everyone for all of the great help and advice I have already received.