You don't have vacuum in the AC system -- all the flaps are vac operated.
This can be because there is a line broken, or because you have a bad servo in the climate control.
Get under the hood and check the green plastic vac lines -- they run next to the brake booster. Make sure they are connected to the manifold and there are no breaks or bad rubber hose bits (this is the usual problem).
If it looks OK, you will then need to pull a vacuum on the climate control and see if it works -- if it works, you have a source problem (most likely a bad connector), if it won' hold vac you will have to track it down.
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!