GF91.30-P-0006RC Airscarf System, Function

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

Function requirements, general
^ C. 15R On
^ Interior temperature T < 40 °C (for code (581) Comfort automatic air conditioning)

The circuit status of circuit 15 is transmitted from the EIS [EZS] control unit (N73) via the interior CAN to the SIH, AIRSCARF and steering wheel heater control unit (N25/7).

Airscarf system, general
The airscarf function permits additional heating of the driver and passenger head area in three stages.

The heated air emerges from an opening in the particular head restraint.

The supply of warm air is dependent on the selected heating stage, the outside temperature, the status of the Vario roof and the vehicle speed (only with Vario roof open).

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

Manual on/off function sequence
The airscarf function is requested by pressing the left AIRSCARF switch (N72/1s21) or the right AIRSCARF switch (N72/1s22) in the upper control panel control unit (N72/1). The status of the corresponding AIRSCARF switch is read in by the upper control panel control unit and transmitted to the AIRSCARF control unit via the interior CAN.

Depending on the request, the AIRSCARF control unit actuates the following components:
- 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 is possible to switch the airscarf system on and off and to a different setting at any time.

The selected heating stage is indicated via red light-emitting diodes in the corresponding AIRSCARF switch.

Press once: Heating stage 3 (3 light-emitting diodes)
Press two times: Heating stage 2 (2 light-emitting diodes)
Press three times: Heating stage 1 (1 light-emitting diode)
Operate four times: AIRSCARF is switched off (no light-emitting diode)

The AIRSCARF fan motors and AIRSCARF heating elements are controlled as a function of the outside temperature, which is detected by the outside temperature indicator temperature sensor (B14). The AIRSCARF fan motors are also controlled as a function of the vehicle speed.

The driver SAM control unit with fuse and relay module (N10/1) reads in the signals of the outside temperature indicator temperature sensor and transmits them on the interior CAN. Information on the vehicle speed is made available by the instrument cluster (A1) on the interior CAN.

The AIRSCARF fan motors are switched on with a time delay and at the maximum control voltage for the duration of t = 0.5 s to avoid voltage peaks and ensure the AIRSCARF fan motors start up safely.

If the airscarf function is switched off again within the switch-on delay period, the fan motors will not run on.

There are two different operating modes depending on the outside temperature.
- Winter operation: temperature range -40 °C to +9 °C
- Summer operation: temperature range +9 °C to +85 °C

If winter operation is disabled via the variant coding, summer operation is used for the entire temperature range.

The temperature limit value between the two operating modes is known as the temperature limit TG.

There is a transition range, temperature hysteresis of TH = 2 °C, in order to avoid fluctuations at the temperature limit.
This ensures that the fan control on cooler days at slow vehicle speeds can be configured such that adequate transmission of heat is achieved.

The following settings can be altered using Star Diagnosis:
- Switch-off threshold
- Temperature limit TG
- Temperature hysteresis TH
- winter operation
- SUMMER OPERATION

When the Vario roof is open, the rotational speed of the AIRSCARF fan motors is increased in all heating stages by an increase in voltage as a function of the vehicle speed. For this purpose, the soft top mechanism control unit (N52) transmits information on the status of the Vario roof via the interior CAN to the AIRSCARF control unit.

When the airscarf function is switched off, the AIRSCARF fan motors are actuated for a period of t = 7 s at the lowest stage to protect the heating elements from overheating.

On vehicles with code (581) Comfort automatic air conditioning, the interior temperature is registered by the in-car temperature sensor (N22/7b1). The comfort AAC [KLA] control and operating unit (N22/7) reads in the in-car temperature sensor signals and transmits them to the interior CAN. The airscarf function is switched off as soon as the interior temperature exceeds a value of T = 40 °C. If there is no valid value available on the interior CAN for the interior temperature, the outside temperature is read in as a substitute value. If a value for the outside temperature is implausible, the airscarf function is switched off.

Automatic switch off function sequence
The airscarf function is switched off if one of the situations listed below occurs:
- Hardware/software defect: If the actuation of the heating elements is detected without the presence of a request or function requirements, the airscarf function is switched off and a fault is stored in the fault memory.
- Defective AIRSCARF fan motor or AIRSCARF heating element:
During the actuation of the AIRSCARF fan motors, the AIRSCARF control unit checks their functionality. For this purpose it evaluates the square wave signals transmitted by the AIRSCARF fan motors.

If the signals are missing or a short circuit or open line is detected at an AIRSCARF fan motor or at an AIRSCARF heating element, the airscarf function is switched off and a fault is stored in the fault memory.

- Hardware overtemperature:
The airscarf function is switched off if the components involved are threatening to overheat. The AIRSCARF control unit continues to operate as per the temperature range definition:
- At a printed circuit board temperature of T > 90 °C, heating stage 3 can no longer be activated.
- At a printed circuit board temperature of T > 100 °C, heating stage 3 and heating stage 2 can no longer be activated.
- At a printed circuit board temperature of T > 110 °C, the airscarf function can no longer be activated.

A fault message is stored in the fault memory if a printed circuit board temperature of T > 110 °C is reached. To switch on again manually, the affected components must have cooled down by T = 2 °C below the corresponding temperature threshold.

- Circuit 15R Off (red traffic light):
The airscarf function is switched off if circuit 15R is switched off. If circuit 15R or circuit 15 is switched on again within a period of t = 5 min, the airscarf function is also activated with the settings that were active last.

- Undervoltage or overvoltage:
If an undervoltage or overvoltage is detected, the AIRSCARF control unit switches off the airscarf function. The light-emitting diode in the switch initially remains switched on. If the on-board power supply voltage reaches its normal voltage again within t = 3 min, the airscarf function is automatically switched on again. However, if the shutoff due to an undervoltage or overvoltage lasts longer than t = 3 min, the light-emitting diode in the AIRSCARF switch is also switched off. If the airscarf function is requested again by pressing the AIRSCARF switch, the light-emitting diode in the AIRSCARF switch lights up for t = 1.5 s and then goes out.

- On-board electrical system limp-home mode:
If the on-board electrical system limp-home mode signal is set by the on-board electrical system management, the airscarf function is switched off.

- Engine starting operation:
The heating elements and the fan motors are switched off during the starting operation. However, the function indicator for the selected heating stage remains set.