Should be a relay labeled "KLIMA" (manufacturer) in the relay box, has about seven connections to it.
If you have a serpentine belt, there is a speed sensor on the compressor, so that if it slows down for any reason, the relay kicks out until you restart the car. This is to prevent the engine getting locked up by a seized compressor.
However, if it blows fuses, check for a short in the wire to the compressor clutch, it sounds like you have a ground somewhere in that wire. Also check for voltage at the wire (unplugged from the clutch) with a new fuse -- if there is voltage there, but the fuse blows when you reconnect the wire, the clutch is shorted and must be replaced.
I don't think a Klima relay will ground out and blow the fuse, but I'm pretty certain a short in the compressor wire will melt the solder in the relay, rendering it inoperative.
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!