AIRSCARF System, Function - GF91.30-P-0008RF

Model 205.4 with code 403 (Heating in head area) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON
• Interior temperature less than 40 °C

The electronic ignition lock control unit sends the status of circuit 15 over the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit.

The climate control, control unit sends the interior temperature over the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit. If a valid interior temperature value is not available, the outside temperature is evaluated as a substitute value.

AIRSCARF, general 

The AIRSCARF function allows the neck area of the driver or the front passenger to be ventilated with warm air at three heating levels. The warm air comes out of an opening below the head restraint.

The AIRSCARF control unit actuates the AIRSCARF function depending on the following variables:

• Selected heating level
• Outside temperature
• Vehicle speed
• Soft top status

Function sequence for AIRSCARF 

The AIRSCARF function is operated using the AIRSCARF switch in the corresponding seat climate control switch group (initial status is AIRSCARF deactivated, all LEDs OFF):

• Press once: 3 LEDs light up, level 3 of heat output activated (heat output 100 %).
• Press twice: 2 LEDs light up, level 2 is activated (heat output 65 %).
• Press three times: 1 LED lights up, level 1 is activated (heat output 35 %).
• Press four times: All LEDs are OFF, the AIRSCARF function is switched off.

The respective front door control unit reads in the status of the AIRSCARF switch over the door-LIN, and sends this over the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit. The AIRSCARF control unit then actuates the following components directly according to the request:

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

The AIRSCARF fan motors are switched on after a 7 s delay. This prevents any cold air from flowing out immediately after activating the AIRSCARF function. For secure start-up of the AIRSCARF fan motors, these are actuated independently of the selected heating level for 0.5 s with the maximum control voltage. During switch-off, the AIRSCARF fan motors run on at the lowest stage for 5 s to protect the AIRSCARF heating elements from overheating.

The AIRSCARF fan motors and the AIRSCARF heating elements are controlled depending on the selected heating stage. 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.

For this, the AIRSCARF control unit receives the following information:

• Outside temperature:

  The front SAM control unit sends the outside temperature value over the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit.

• Vehicle speed:

  The instrument cluster sends the displayed vehicle speed over the user interface CAN, electronic ignition lock control unit, the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit.

• Soft top status:

  The rear control unit sends the soft top status over the interior CAN, rear SAM control unit and the heater LIN to the AIRSCARF control unit.

Function feedback: 

The AIRSCARF control unit sends the corresponding status over the heater LIN, rear SAM control unit, interior CAN, front door control unit and the door-LIN to the respective seat climate control switch group for feedback on the function. Each seat climate control switch group actuates the corresponding LEDs in the AIRSCARF switch directly.

Shutoff criteria: 

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

• Shutoff in the event of a hardware defect: 

  If the AIRSCARF control unit reports an active actuation of the AIRSCARF heating elements to the rear SAM control unit although a request has not been issued by the AIRSCARF switch, the power supply of the AIRSCARF heating elements is switched off by an integrated protection relay from the rear SAM control unit.

• Shutoff in the event of overtemperature of the printed circuit board: 
  • At a printed circuit board temperature of more than 90 °C, heating level 3 can no longer be activated.
  • At a printed circuit board temperature of more than 100 °C, heating level 3 and heating level 2 can no longer be activated.
  • At a printed circuit board temperature of more than 110 °C, the AIRSCARF function is switched off.

  When a printed circuit board temperature of more than 110 °C is reached, a fault message is stored in the fault memory. Manually switching back on requires the affected components to cool down to a value of 2 °C below the corresponding temperature threshold.

• Shutoff in the event of an error (short circuit, overload or open circuit (line break)): 

  The AIRSCARF control unit constantly monitors the functional capability of the corresponding components, and sends the status to the rear SAM control unit. If the signals are not received or if short circuit or an open circuit is detected on an AIRSCARF fan motor or on an AIRSCARF heating element, the power supply for the components is deactivated and a fault stored in the rear SAM control unit fault memory.

• Shutoff during engine starting procedure: 

  During the starting procedure of the engine, the AIRSCARF heating elements and the AIRSCARF fan motors are switched off. The LEDs in the AIRSCARF switch remain switched on for the selected heating level.

• Switching off by energy management: 

  In order to prevent the battery from discharging in all driving cycle phases, the state of charge is continuously evaluated. Depending on the situation, the AIRSCARF function is also deactivated. If the AIRSCARF function is switched off, the LEDs initially remain switched on. If the on-board electrical system reaches its on-board electrical system voltage again within the next 3 minutes, the AIRSCARF function is also automatically started. If the shutoff takes longer than 3 minutes, the LEDs are also switched off. If the shutoff continues and the function is requested again, the LEDs illuminate for 1.5 seconds and then they go off.

• Shutoff after circuit 15R OFF: 

  At circuit 15R OFF and circuit 15C ON, the timer control runs on for 5 minutes. If circuit 15R is switched on again during this period, the AIRSCARF function is also switched on again.

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