GF91.30-P-0006RI Airscarf System Function

GF91.30-P-0006RI Airscarf System Function
- with CODE (403) Airscarf system

Function requirements, general
^ C. 15R On
^ Interior temperature T < 40 °C

The circuit 15 status is sent by the EIS [EZS] unit (N73) over the interior CAN to the AIRSCARF control unit (N25/7).

AIRSCARF system in general
The AIRSCARF system enables additional heating of the driver and front passenger headroom.

The heated air emerges from an opening in the particular head restraint. The warm-air supply depends on the selected heater stage, the outside temperature, status of the Vario roof and the vehicle speed (opened Vario roof only).

The AIRSCARF system consists of the following subfunctions:
^ Manual on/off function sequence
^ Automatic switch off function sequence

Manual on/off function sequence
Pressing the left AIRSCARF switch (S91/2s21) in the left seat adjustment switch group (S91/2) is read in by the left door control unit (N69/1) and the request sent over the interior CAN to the AIRSCARF control unit.

Pressing the right AIRSCARF switch (S92/2s21) in the right seat adjustment switch group (S92/2) is read in by the right door control unit (N69/2) and the request sent over the interior CAN to the AIRSCARF control unit.

The AIRSCARF control unit then actuates the following components in accordance with the relevant request:
- Left AIRSCARF heating element (R22/5) and
- Left AIRSCARF fan motor (M4/10)

or:

- Right AIRSCARF heating element (R22/6) and
- Right AIRSCARF fan motor (M4/11)

It can be switched on, over and off at any time.

The selected heating stage is indicated by the red LEDs lighting on the corresponding AIRSCARF switch:
Press once: Heating stage 3 (3 LEDs on)
Press two times: Heating stage 2 (2 LEDs on)
Press three times: Heating stage 1 (1 LED on)
Operate four times: AIRSCARF system switched off (LEDs OFF)

Actuation of the fan motors and heating elements takes place depending on the outside temperature, which is recorded by the outside temperature indicator temperature sensor (B14). The fan motors are also actuated depending on the vehicle speed. The driver SAM control unit (N10/10) reads in the signals of the outside temperature indicator temperature sensor and sends them to the interior CAN. Information on vehicle speed is made available by the instrument cluster (A1) on the interior CAN.

The fan motors are switched on with a delay and for t = 0.5 s at maximum control voltage, to avoid any peak stresses and to ensure that the fan motors start up without any problems.

If during the switch-on delay period, they are switched off again, the fan motors will not run on.

Depending on the outside temperature a differentiation is made between two operating modes.
- Winter operation: temperature range -40 °C to +9 °C
- Summer operation: temperature range +9 °C to +85 °C

If winter operation is deactivated using variant coding, summer operation is valid throughout the entire temperature range.

The temperature limit between the two operating modes is designated as the temperature limit T L.

To avoid any fluctuations in the temperature limit, a temperature hysteresis TH = 2 °C is provided.

This serves to ensure that the fan control on cooler days at lower vehicle speeds is configured such that sufficient transmission of heat is provided.

The following settings can be changed using STAR DIAGNOSIS:
- Switch-off threshold
- Temperature limit TL
- Temperature hysteresis TH
- Winter operation
- Summer operation

When the Vario roof is open, the speed of the fan motors is raised in all heating stages depending on the vehicle speed by increasing the voltage. To this end, the roll bar Vario roof control control unit (N52) sends data on the Vario roof status over the interior CAN to the AIRSCARF control unit.

During switch off, the fan motors are actuated in the lowest stage for t = 10 s to protect the heating elements against overheating. The interior temperature is recorded by the in-car temperature sensor (N70b1) in the overhead control panel control unit (N70). The overhead control panel control unit sends the corresponding information over the interior CAN to the AIRSCARF control unit. As soon as the interior temperature exceeds the switch-off threshold value of T = 40 °C, the AIRSCARF function is switched off. If a valid value for the interior temperature is not present on the interior CAN, the outside temperature is used as a substitute value. In the event of an implausible value for the outside temperature, the AIRSCARF system is switched off.

Automatic switch off function sequence
When one of the following situations occurs, the AIRSCARF function is switched off:
- In the event of a hardware/software fault:
If actuation of the heating elements is detected without any pending request or function requirements, then the AIRSCARF function is switched off and a fault stored in the fault memory of the AIRSCARF control unit.

- In the event of a defective fan motor or heating element:
During actuation of the fan motors the control unit checks them for functional availability. To this end, it also evaluates the square wave signals sent by the fan motors.

If the signals are not received or if short circuit or an open circuit is detected on a fan motor or on a heating element, the AIRSCARF system is switched off and a fault is stored in the fault memory of the AIRSCARF control unit.

- In the event of excess hardware temperature:
In the event of imminent overheating of the involved components, the AIRSCARF function is switched off. The AIRSCARF control unit continues to operate in accordance with the temperature range definition:
- Heating stage 3 can no longer be activated if the PCB temperature is T > 90 °C.
- Heating stage 3 and heating stage 2 can no longer be activated if the PCB temperature is T > 100 °C.
- The function can no longer be activated if the PCB temperature is T > 110 °C.

If the PCB temperature reaches T > 110 °C, a fault message is stored in the fault memory. Before switching back on manually, the components concerned have to have cooled down to T = 2 °C below the corresponding temperature threshold.

- At circuit 15R OFF:
When switching off circuit 15R, the AIRSCARF system is switched off. If circuit 15R or circuit 15 is switched on again within t = 5 min, then the function is performed using the last active settings.

- At undervoltage or overvoltage:
In the event of any detected undervoltage or overvoltage, the AIRSCARF control unit switches off the function. The LED for the AIRSCARF switch initially remains on. If the on-board power supply voltage returns to its normal level within t = 3 min, the AIRSCARF function is automatically switched on again. If the deactivation as a consequence of undervoltage or overvoltage lasts longer than t = 3 min, the LED in the AIRSCARF switch is also switched off. If the AIRSCARF function is requested again by pressing the AIRSCARF switch, the LED in the AIRSCARF switch lights up for t = 1.5 s before going out.

- In the event of an on-board electrical system emergency operation:
If the on-board electrical system management sets the on-board electrical system emergency operation signal, the AIRSCARF system is then switched off.

- During engine startup:
During the startup process, the heating elements and the fan motors are switched off. The function indicator for the selected heating stage remains active however.