When this relay is picked, power from Pin_4 is routed to Pin_1 and the AC clutch/Rad Fan is activated. When AC clutch/Rad Fan is deactivated, the winding of the wires within the coil/motor can cause a large voltage spike unto the circuit. Note Pin_1 is routed to Pin_3 and to ground. This configuration will tie both ends of the AC clutch/Rad Fan to ground. I believe this is added protection for the clutch diode.