The relays T6 and T7 for the engine compartment junction unit B1 manage the engagement of the fans N11 and N12 at two speeds: the coils are supplied by the line controlled by the ignition (15/54) whilst the power lines are protected by fuses F6 and F7, in the engine compartment junction unit B1.Both are energized by a control signal - earth - coming from the engine control unit M10, pins 90 and 69 of connector A, respecitvely. The coil for the remote control switch J29 is supplied by the direct line protected by fuse F18 in the engine compartment junction unit B1. Linear sensor K120 receives a power supply and reference earth from the engine management control unit M10, pins 12 and 22 of connector A.If the engine coolant reaches a first temperature level, or the linear sensor K120 indicates to the control unit M10 - pin 13 of connector A - that a certain pressure level has been reached, the control unit M10 sends a signal - from pin 90 of connector A which energizes the fan 1st speed relay T6; the relay T6 then sends a supply to the fan N11 which, with remote control switch J29 not energized, finds itself in series with the fan N12: both therefore rotate at the first speed. If the coolant reaches a higher temperature level, or the linear sensor K120 indicates to the control unit M10 that a higher pressure has been reached, the control unit M10 sends a signal - from pin 69 of connector A - to the fan 2nd speed relay T7 and, at the same time, to remote control switch J29; this signal energizes the coils: relay T7 then sends a supply directly to the fan N12 which rotates at maximum speed; the remote control switch J29 , on the other hand, sends a supply directly to the fan N11 : the two fans are in parallel and rotate at maximum speed.