You have your climate control figured out. In the normal position the system will turn on ac or heat depending upon what is needed. EC is the same except it uses outside air, no ac.
If everything is okay, put fan on auto, push normal button, set the temperature you like and forget about it. Five years from now you will figure this out all over again because you will not have touched the controls unless something has gone wrong, or you had to use the defroster. When working properly, this climate control is that good.
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in