I'd agree with JH -- if the aux fan isn't running, and the visco clutch is weak, the temp will get too high and the compressor will shut off until the high side temp comes down. This is to prevent stalling from high pressure, and blowing the high side AC hoses (I've done it, because the aux fan wasn't working on the 220D).
Check the fuse for the aux fan, and make sure it runs when you unplug and cross the temp sensor wires on the receiver dryer, and that when you unplug the temp sensor in the middle of the head that the aux fan runs.
Chances are the visco clutch is empty, too.
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!