AIRSCARF system, function - GF91.30-P-0006CA

MODEL 207.4 with CODE 403 (Airscarf system)

Fig 1: AIRSCARF System Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Circuit 15R ON
Interior temperature T < 40 °C

The electronic ignition lock control unit sends the status of circuit 15 via interior CAN to the AIRSCARF system control unit.

The automatic air conditioning control and operating unit sends the interior temperature via interior CAN to the AIRSCARF system control unit. If there is no valid value available for the interior temperature then the outside temperature is evaluated as a substitute value.

AIRSCARF, 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 Airscarf function takes place via the AIRSCARF system control unit depending on the following variables:

Selected heating level
Ambient temperature
Soft top status
Vehicle speed

Function sequence for AIRSCARF

The operation of the AIRSCARF function occurs via the AIRSCARF buttons in the upper control panel control unit. The upper control panel control unit reads in the status of the corresponding AIRSCARF button directly and sends this via instrument panel LIN, front SAM control unit and interior CAN to the AIRSCARF system control unit.

The AIRSCARF system control unit actuates the following components according to the request:

Left AIRSCARF heating element
Right AIRSCARF heating element
Left AIRSCARF fan motor
Right AIRSCARF fan motor

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 red light-emitting diodes (LEDs) lighting up in the respective AIRSCARF button.

Pressing once: Heating stage 3 (100 % heat output, three LEDs light up)

Pressing twice: Heating stage 2 (65 % heat output, two LEDs light up) Pressing three times: Heating stage 1 (35 % heat output, one LED lights up)

Pressing four times: AIRSCARF is switched off (no LEDs light up) The AIRSCARF system control unit sends the corresponding status via interior CAN, front SAM control unit and instrument panel LIN to the upper control panel control unit. The upper control panel control unit actuates the LED in the respective front seat heater button directly. 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.

Here the AIRSCARF system control unit receives the following information:

The outside temperature is recorded by the outside temperature sensor. The front SAM control unit directly reads in the resistance value of the outside temperature sensor, calculates the outside temperature and sends this via interior CAN to the AIRSCARF system control unit. If a value for the outside temperature is implausible, the airscarf function is switched off.
The status of the soft top is sent by the rear control unit via interior CAN to the AIRSCARF system control unit.
The vehicle speed is sent by the instrument cluster via interior CAN to the AIRSCARF system control unit.

When one of the following situations occurs, the AIRSCARF function is switched off automatically:

Shutoff after circuit 15R OFF:
With circuit 15R OFF and circuit 15C ON, the timer control runs on for another t = 5 min. If circuit 15R is switched on again, the AIRSCARF function is also switched on again.
Deactivation with undervoltage or overvoltage:
If undervoltage or overvoltage is detected, the AIRSCARF system 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.
Shutoff in the event of a hardware defect:
If the AIRSCARF heating elements are actuated without any pending request or function requirement, the AIRSCARF function is switched off and a fault stored in the fault memory of the AIRSCARF system control unit.
Switching off in the event of a defective AIRSCARF fan motor or AIRSCARF heating element:
During actuation of the AIRSCARF fan motors, the AIRSCARF system control unit checks their functional availability. It evaluates the square pulses sent 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.
Shutoff in the event of hardware overtemperature:
In the event of a risk of overheating of the involved components, the AIRSCARF function is switched off.
Shutoff in the event of 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.
Shutoff when the engine starts:
During the starting procedure of the engine, 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.
Shutoff in the event of overtemperature of the printed circuit board: 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.

With a printed circuit board temperature T > 110 °C, the AIRSCARF function is switched off.

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.

	Electrical function schematic for AIRSCARF		PE91.30-P-2051-97EAA
	Overview of system components of comfort heating systems		GF91.30-P-9990CAM