The additional heater unit N140 is connected to the vehicle electrical system by means of connector D22A direct power supply reaches the unit N140 - pin 1 of connector B - via the line protected by maxifuse PTC2, located on the battery, connector B99, pin 2, on the other hand, is earthed.Pin 3 of connector A of N140, on the other hand, is connected to the outside air temperature sensor K79 which, in turn receives a reference power supply from the alternator (pin D+ alternator signal A10, pin 19 of connector A of M1 - : in this way the outside temperature signal is only sent to the additional heater control unit if the engine is running.The on signal reaches pin 1 of connector A of N140 from the remote control receiver M74This receiver receives a supply from a direct line, protected by fuse F39 of the junction unit under the dashboard B2 .The inertia switch I50 earth signal reaches pin A of the pump N44 and, in the case of an impact, the intertia switch interrupts the circuit and prevents a supply of fuel which would be dangerous; the pump is then controlled - pin B - by the control unit N140 from pin 6 of connector A.The additional heater control unit has an autodiagnostic system which can be used: by connecting to connector R10 : the signals from pin 2 of connector arrive via the K diagnostic line See E8010 DIAGNOSTIC MULTIPLE CONNECTOR.The additional heater control unit M75 controls the engagement of the fan N85 with the heater on: a special signal reaches pin 4 of M75 from pin 4 of connector A of N140.The control unit M75 receives an ignition-operated power supply (INT/A) - pin 5 - from the line protected by fuse F31 of the junction unit under the dashboard B2 and controlled by relay T8 and fuse F8 of the engine compartment junction unit B1; the ignition-operated power supply (INT) - pin 2 - arrives via the line protected by fuse F49 of the junction unit under the dashboard B2 .The power supply reaches pin 8 from the line with the special fuse B38; pin 3 is earthed.The signal for switching on the fan N85 leaves pin 9 of M35.