Possibly the Klima relay (behind the battery) or the climate control push button unit (PBU). There are 2 switches on the dryer behind the left headlight. One has connectors on pigtails, the other has connectors right on the sensor. Pull one of the wires from the sensor - switch, actually - without pigtails. If the compressor disengages, the problem is with the PBU. If the compressor keeps running, the problem is with the Klima relay.

Sixto
87 300D^2