To say nothing of frying a compressor low on freon.....
Leading cause of compressor dropout is a bad speed signal, usually caused by a slipping belt. This in turn is usually a bad belt tensioner, the rubber part croaks. Pricey, but you will only need one for the next 200,000 miles.
Unwire it, connect correctly, and check the refrigerant pressures, then see what it does. Lots of talk about AC this summer, surely you will find something. If not, post again!
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!