The compressor activation circuit is controlled by relay R5, contained in engine bay junction unit B001. This is supplied directly by a line from the battery that enters at pin 1 of control unit connector A and is protected by fuse F19.The coil of relay R5 is supplied by a signal from relay R9 that in turn receives a direct power supply from the battery from pin 1 connector A.Relays R9 and R5 are excited by an earth signal from engine compartment control unit M10 from pins 72 and 79 of connector A respectively.In this way, control unit M10 controls the activation of air conditioner compressor L20 through relay R5.Engine control unit M10 connector a receives signals from the 4 level pressure switch K10 to turn on the radiator fan:- operation at first speed from pin 58;- operation at second speed from pin 81;- air conditioner activation from pin 54.