On the driver and passenger side, separate choices can be made between 3 different automatic blower settings (LOW, MED and HIGH) and a MAX position.
For ventilation of the rear compartment, two additional blowers are installed beneath the front seats. The blower output is set by means of two rotary blower switches whose position is evaluated by the control unit. The function logic - if necessary - influences the setpoint values. The output driver issues a corresponding control voltage.
Without dynamic pressure compensation, as the driving speed increases, the air volume at the air inlet duct also increases disproportionately. This effect can be compensated if the fresh air flap, controlled by the speed signal (K CAN message), reduces the size of the air inlet channel. In order to prevent continuous movement of the flap due to slight vehicle speed changes, the nominal position is calculated from the speedometer signal with a delay.
The ram pressure characteristic curve is extended to create a characteristic map by including the blower output.
The blower output is raised or lowered under certain circumstances:
In order to be able to cool down or heat up the interior in the case of extreme interior temperatures, the blower output is raised automatically depending on the setting for the driver area.
The maximum blower value is limited depending on the coolant temperature.
If the vehicle voltage drops below a certain limit value, the power module initiates a reduction in the blower output via the body CAN SYSTEM.
In order to relieve the load on the car battery during the starting sequence, the blower is switched off. A defect in the bus transmission of the message ”terminal 50”, however, could shut down the blower. This is why the duration of the active state is evaluated. The status ”terminal 50 physically on” is inverted if:
The previous status is then regarded as invalid. No fault entry is made in the fault memory, but the function is then ”logically off”. The blower deactivation remains inactive until terminal 15 drops. In the case of terminal 15 new start, the blower deactivation becomes active again.
The setpoint value of the rear compartment blower is influenced by the function logic depending on the current ambient conditions:
Rear compartment blower OFF with:
Limitation to 25% setpoint activation by:
If none of the above conditions applies, the setpoint value determined by the input driver is forwarded without change to the output driver.