SAAB WIS ONLINE

Electrically heated rear window, detailed description, 4D

Electrically heated rear window, detailed description, 4D

Cars with ACC:


The heated rear window is activated by pressing the corresponding switch. The switch is integrated in the ACC panel. The function can also be activated automatically by ACC.

When the heated rear window switch is depressed, the ACC control module sends out the bus message "Rear demist request from ACC", which is used by BCM. If the ignition key is in the ON position and the car engine is running, BCM will transmit the bus message "Rear demist request" after a 5-second delay. BCM will transmit this message as long as the above conditions are met or until 12 minutes have elapsed.


The bus message "Rear demist request from ACC" is used by REC, which activates rear window relay 113. B+ is then fed from REC pin 2, which in turn is connected to the antenna amplifier.

In the antenna amplifier, current passes through a coil with low resistance, is directed on to the rear window heating conductors, and is grounded via an antenna filter (coil). The coils on both sides are intended to prevent high-frequency signals (88-108 MHz) from being grounded and then directed out through the combined rear window/antenna.

At the same time REC (701) activates the output to the heated rear window, it also sends out the bus messages: "Rear demist", which is used by ACC to light the symbol in the display, and "Rear electrical centre, change in current consumption", which is used by the engine management system to compensate for the increased generator load.

Cars with MCC

The heated rear window is activated by pressing the corresponding switch. The switch is integrated in the MCC panel. When the heated rear window button is pressed, MCC grounds pin 7, which is connected to BCM pin 57. If the ignition key is in the ON position and the car engine is running, BCM will transmit the bus message "Rear demist request from BCM". BCM will transmit this message with a 5-second delay as long as the above conditions are met or until 12 minutes have elapsed.


The bus message "Rear demist request from BCM" is used by REC which in turn activates relay 113. B+ is then fed from REC pin 2, which in turn is connected to the antenna amplifier.

In the antenna amplifier, current passes through a coil with low resistance, is directed on to the rear window heating conductors, and is grounded via an antenna filter (coil). The coils on both sides are intended to prevent high-frequency signals (88-108 MHz) from being grounded and then directed out through the combined rear window/antenna.

At the same time REC activates the output to the heated rear window, it also sends out the bus messages: "Rear demist", which is used by BCM (BCM sends out B+ which is connected to MCC pin 22 and the LED lights) and "Rear electrical centre, change in current consumption", which is used by the engine management system to compensate for the increased generator load.