841003978 - E3030 DEMISTING REARSCREEN AND REAR VIEW MIRRORS DESCRIPTION

Description

In the case of poor visibility it is possible to activate the demisting of the rearscreen, the exterior rear view mirrors and the windscreen. The control button, located on the climate control system control unit, sends a signal via the CAN to the Body Computer which, depending on the logics described later on, manages the heating of the resistances for the components. These resistances absorb a considerable amount of energy and are therefore controlled and, possibly, deactivated after they have been working for a certain length of time.The activation of the demisting function for the rearscreen, rear view mirrors and windscreen can only occur if the INT (+15) signal is present. The Body Computer acquires this condition during starting (INT/A) and does not energize the relay inside the junction unit under the dashboard.The deactivation of the demisting function, on the other hand, is possible:

  • manually: by pressing the unstable button on the climate control system control unit again or if there is no INT (key-off) signal;
  • automatically: after 20 minutes effective operation with the control activated.
The automatic operation of the device is also linked to the engine speed; the switching on/off logic is as follows:

  • the first ten minutes operation is not dependent on the engine speed;
  • the period after this depends on the engine conditions, namely: if the engine speed is below 950 rpm, then the device should be switched off after 10 seconds;
  • if, on the other hand, the engine speed is above 1000 rpm for at least 5 seconds, then the rearscreen and the other components can be switched on or remain switched on if they are already on until they have been working effectively for 20 minutes.
The automatic activation of the demisting function is also determined by the outside temperature conditions: the Body Computer acquires information concerning the outside temperature, via the CAN, from the sensor inside the driver''s rear view mirror and, if the temperature is below the level of 3 degrees, then the rearscreen, the exterior rear view mirrors and the windscreen need demisting.During the entire period of automatic operation the heated rear windscreen relay should be switched off if the battery voltage goes below 8.5V for 0.5 seconds.The relay is restored when the battery voltage increases to 9V for a period of half a second. A tolerance of ±5% applies to all the values describedThe automatic activation cycle (20 minutes) is restored each time a command is received via the special button.The heated rear windscren warning light is managed by the climate control system control unit depending on the command send via the CAN from the Body Computer. During automatic operation the warning light should remain on constantly, even during periods in which the demisting function may be deactivated, following the logic described previously.When the MAX-DEF control is activated using the button on the climate control system control unit, it is possible to activate the functions of switching on the heated rear windscreen, demisting the windscreen (with the possibility of manually increasing or decreasing the speed of the fan) and the forced recirculation of the air, all for a predefined period which starts the moment the engine coolant reaches operating temperature    See E5020 ENGINE COOLINGThe deactivation of the MAX-DEF control only involves switching off the heated rear windscreen if the command to switch it on came from the MAX-DEF button; if, on the other hand, the command was given via the heated rear windscreen button, it remains on.