Glad I could help with post from manual. Mine is actually 300D mentioned in signature. Your 190E is different.. perhaps you could find a book that will fully explain your buttons etc. and let us all know. I drove a 190E that I was interested in purchasing (years ago) and the odd thing about the AC to me was that when I pushed the accelerator down to get power quickly, the compressor shut off.. warm air coming from the vents.. when I reached speed and leveled off.. cold air came from vents. I just wondered if this was a way to get more power for the 190E? I wondered if there was an automatic cutoff when you needed power and then reinstated after you achieved your steady speed, or if it was just a quirk of the car I drove. I still don't know the answer, but did like the car a lot.
Oh, and just for the record, when I was 16 and very interested in "wheels", AC was not common on cars. We had to get a car with AC because my father had asthma and AC would be better for him. When reading the book on Buick LeSabre, they said NORM was the most efficient way to run the AC; RECIR was for "in town" driving when air was not being forced into the car from highway speeds. Once achieving steady highway speed, we were to switch to NORM. RECIR was called MAX on some other models of US cars. I have no idea why it was more efficient, just what the book said. Since you get mileage with MAX, maybe the systems have been reconfigured.
1982 300D (266,001 mi.) looking and running great
1976 450 SLC
1982 Jaguar XJ6 (loved, but gone)