The relays J30, J31and J32located next to the engine management control unit manage the engagement of the two fans N11and N12at two speeds: the coils are supplied by the line for fuse F6 of the engine compartment junction unit B1A.The relays are energized by an earth signal coming from the engine management control unit M10.If the engine coolant reaches an initial temperature level, or the 4 stage pressure switch K10signals to the control unit M10pin 9 of connector A - that the initial pressure level has been reached, then the control unit M10sends a signal from pin 50 of connector A to the 1st speed relay J30, which then sends the power supply to the fan N11via the additional resistance O10and to the fan N12via the additional resistance O12: the two fans turn at the first speed (slow).If the engine coolant reaches a higher temperature level, or the 4 stage pressure switch K10signals to the control unit M10pin 41 of connector A that the higher pressure level has been reached, then the control unit M10sends a signal from pin 62 of connector A to the two 2nd speed relays J31and J32, which then send the power supply to the fan N11and to the fan N12directly: the two fans turn at the maximum speed.