Larry has the AC correct. The temp control is colder the farther clockwise it is turned.
If you don't get any cooling, check the charge. You can convert to 134a without any problems.
The heater/vent controls are as follows:
Upper left lever, vent and blower. Right, off, four steps to the left: 1) airflow on 2) blower low, 3) blower medium 4) blower hight
Upper right lever: Air distribution left, windshield, right, floor
Lower levers: Heat control for appropriate side. toward center, off, cold. toward outside of panel, hot. (the work oppsite each other).
Levers for side vents: Up, open, down closed. These blow unconditioned air only, I think.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!