Sounds like the compressor speed signal isn't correct or the Klima (or MAS) relay is bad.
You will need to find someone who understands the compressor control system on this car. The compressor control relay (KLIMA, usually) gets inputs from the speed sensor in the compressor, the crank position sensor, the temp switch on the evaporator, the PBCU, and the temp sensor on the engine and decides when to turn the compressor on based on those inputs.
You also need to verify that the compressor clutch is good. Ditto for serpentine belt and tensioner.
Usually, a slipping belt or bad speed sensor signal will cause the AC compressor to run for a minute or less, then shut off until you turn the ignition off and back on, so something else is going on here.
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!