GF91.30-P-0006CA AIRSCARF System, Function

GF91.30-P-0006CA AIRSCARF System, Function


Function requirements, general
- Circuit 15R ON
- Interior temperature T < 40 °C

The electronic ignition lock control unit (N73) transmits the status of circuit 15 via the interior CAN (CAN B) to the AIRSCARF system control unit (N25/7).

AIRSCARF system in general
The airscarf function allows ventilation of the neck area of the driver or the front passenger with heated air at three heating levels. The warm air comes out of an opening below the respective head restraint.

Controlling of the function Airscarf takes place via the AIRSCARF system control unit depending on the following variables:
- Selected heating level
- Interior temperature
- Ambient temperature
- Soft top status
- Vehicle speed

The airscarf function consists of the following subfunctions:
- Function sequence for manual on/off
- Function sequence for automatic switch off

Function sequence for manual on/off
The function Airscarf is requested by actuating the left AIRSCARF button (N72/1s21) or the right AIRSCARF button (N72/1s22) in the UCP control unit (N72/1).
The UCP control unit reads in the status of the respective AIRSCARF button and transmits this via the instrument panel LIN (LIN 1), front SAM control unit with fuse and relay module (N10/1) and interior CAN to the AIRSCARF system control unit.

The AIRSCARF system control unit actuated the following components according to the request:
- Left AIRSCARF heating element (R22/5) or right AIRSCARF heating element (R22/6)
- Left AIRSCARF fan motor (M4/10) or 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.

Switching on of the AIRSCARF fan motors is delayed for t = 7 s.
This prevents streaming out of cold air immediately after activation of the function Airscarf.
This is actuated independently of the selected heating level for t = 0.5 s with the maximum control voltage for secure start-up of the AIRSCARF fan motors. During switch off, the AIRSCARF fan motors are set to the stage for t = 5 s to protect from overheating of the AIRSCARF heating elements.
If the AIRSCARF function is switched off again within the switch-on delay period, the AIRSCARF fan motors will not run on.

The selected heating level is displayed by lighting up red LEDs (LED) in the respective AIRSCARF button:
Actuated once: Heating level 3 (3 LEDs)
Actuated twice: Heating level 2 (2 LEDs)
Actuated three times: Heating level 1 (1 LED)
Actuated four times: The function AIRSCARF is switched off (all LEDs off)

Controlling of the AIRSCARF fan motors and the AIRSCARF heating element takes place depending on the selected heating level. The rotational speed of the AIRSCARF fan motors is also controlled for an opened soft top depending on the vehicle speed and the outside temperature.

The AIRSCARF system control unit receives the following information for this via the interior CAN and evaluates these:
- The interior temperature is detected by the interior temperature sensor (B10/4) and prepared for use by the AAC control and operating unit (N22/7)
- The outside temperature is detected by the outside temperature sensor (B14) and read in and prepared for use by the front SAM control unit
- Status of the soft top from the rear control unit (N22/6)
- Vehicle speed from instrument cluster (A1)

The function Airscarf is switched off for an interior temperature of T 40°C. If there is no valid value available for the interior temperature then the outside temperature is evaluated as a substitute value. If a value for the outside temperature is implausible, the airscarf function is switched off.

Function sequence for automatic switch off
When one of the following situations occurs, the AIRSCARF function is switched off automatically:
- In the event of a hardware/software fault:
If actuation of the AIRSCARF 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 system control unit.

- Defective AIRSCARF fan motor or AIRSCARF heating element:
During actuation of the AIRSCARF fan motors, the AIRSCARF control unit checks their functionality. It evaluates the level of the DC signal transmitted by the AIRSCARF fan motors for this purpose. If the signals are not received or if short circuit or an open circuit is detected on a AIRSCARF fan motor or on a AIRSCARF heating element, the AIRSCARF function is switched off and a fault stored in the fault memory of the AIRSCARF system control unit.

- In the event of an excessively high hardware temperature:
In the event of imminent overheating of the involved components, the AIRSCARF function is switched off.
The AIRSCARF system 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.

- Circuit 15R off:
The AIRSCARF function is switched off if circuit 15R is switched off. The timer control continues to run for t = 5 min as long as circuit 15C is switched on. If the circuit 15R is switched on again during this time the AIRSCARF function is set to the last active condition.

- Heating stage 3 and heating stage 2 can no longer be activated if the PCB temperature is T > 100°C.
- At a printed circuit board temperature of T > 110°C, the airscarf function can no longer be activated.

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.

- Undervoltage or overvoltage:
If an undervoltage or overvoltage is detected, the AIRSCARF control unit switches off the AIRSCARF function.
The LED in the AIRSCARF button remains switched 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 button is also switched off. If the AIRSCARF function is requested again by pressing the AIRSCARF button, the LED in the AIRSCARF button lights up for t = 1.5 s before going out.

- On-board electrical system emergency operation:
If the On-board electrical system management activates on-board electrical system emergency operation, the AIRSCARF system control unit switches the AIRSCARF function off.

- During engine startup:
During the startup process, the AIRSCARF heating elements and the AIRSCARF fan motors are switched off. The LED in the AIRSCARF button remains set at the selected heating level.