I have a similar problem with my '85 300D only that its only an occasional one. Sometimes when I turn on the "EC" button to just have the fan blow, even with the coldest setting, it'll blow hot air. The only thing that sometimes takes care of the problem is when I turn on the A/C long enough to cool the air down in the car and then go back to "EC' mode, the hot air problem goes away.
Any ideas?
