The relay T5 in junction unit B1Bcontrols the compressor engagement circuit.The supply for relay arrives from the line for maxifuse JB/3 of B5, via the line for the specific fuse F1 in junction unit B1A.The supply for the coil for relay T5 arrives from the main injection relay T9, located in junction unit B1B See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT.The climate control system control unit M70sends - from pin 36 - the enablement signal for engaging the compressor, to the 4 stage pressure switch K10: if the pressures in the coolant circuit are correct, the signal leaves the pressure switch and reaches the engine management control unit M10, pin 6 of connector A. On the basis of its internal control logic, the control unit M10sends the command - from pin 13 of connector A - to engage the compressor which energizes the relay T5 so that the air conditioning compressor engagement solenoid L20 is operated at a voltage of 12 V .