In the old days I heard the pressure switch on the Reciever/Dryer referred to as a low pressure cut out switch.... meaning a sensor designed to stop cycling the compressor when the refrigerant has leaked out... and no lubricant would be making its way back to the compressor...
So there is a chance that the fan is operated by the temp switch on the Reciever/dryer and the one on the block... since it is a dual function fan... a check of the wiring schematic should prove this one way or another....