Comfort Displays, Function - GF54.30-P-3043RF

Model 205, 253 

Function requirements in general 

• Instrument cluster (A1) activated

Comfort displays in general 

The comfort displays provide a quick overview of the following information:

• Function sequence for displaying outside temperature 
• Function sequence for displaying the time 
• Function sequence for scale illumination of instrument cluster 

Function sequence for displaying outside temperature 

The outside temperature is detected by the outside temperature sensor (B14).

The front SAM control unit (N10/6) reads in the signals of outside temperature sensor directly, calculates the outside temperature and sends this to the instrument cluster via interior CAN (CAN B), electronic ignition lock control unit (N73) and user interface CAN (CAN HMI). The outside temperature is displayed in the multifunction display (A1p13) of the instrument cluster in °C, in accordance with the country coding.

The following parameters must be considered in addition so that the actual outside temperature is displayed:

• Vehicle speed (falsification of value through air stream)
• Coolant temperature (falsification of value through radiant heat)

The vehicle speed is calculated on the basis of the wheel speeds.

The Electronic Stability Program control unit (N30/4) transmits the information about the wheel speed over the suspension FlexRay (Flex E), the electronic ignition lock control unit and the user interface CAN to the instrument cluster.

The CDI control unit (N3/9) (with diesel engine) or the ME-SFI control unit (N3/10) (with gasoline engine) transmits information about coolant temperature via the engine CAN (CAN C), the powertrain control unit (N127), the chassis FlexRay, the electronic ignition lock control unit and the user interface CAN to the instrument cluster.

The coolant temperature values exert the following influence on the outside temperature display:

• Coolant temperature T < 60 °C:

  The current outside temperature value is always shown.

• Coolant temperature T > 60 °C and "Engine running" or "Drivetrain operational" signal is set:

At vehicle speeds of v < 20 km/h (with vehicle deceleration), the outside temperature display is only changed if the measured outside temperature value drops. At vehicle speeds of v = 20 to 45 km/h, rising outside temperatures are displayed after a delay period of t = 3 minutes.

At vehicle speeds of v > 45 km/h, rising outside temperatures are displayed after a delay period of t = 90 seconds.

The CDI control unit or the ME-SFI control unit sends the "engine running" or "drivetrain operational" signal via the drivetrain CAN (CAN C1), powertrain control unit, chassis FlexRay, electronic ignition lock control unit and user interface CAN to the instrument cluster.

If the vehicle speed signal is faulty, rising outside temperatures are updated and shown in an attenuated manner every t = 10 minutes.

• Coolant temperature T > 60 °C and "Engine running" or "Drivetrain operational" signal is not set:

A delay period of maximum t = 1 h prevents an apparent increase in outside temperature from being displayed that is caused by heat dissipated from the engine. A rise in display value is not permitted during this delay period. With circuit 15 OFF, the last measured outside temperature value is stored and then displayed when the circuit is reactivated. The electronic ignition lock control unit sends the circuit 15 status to the instrument cluster via user interface CAN.

If, in the meantime, the measured outside temperature has dropped below the stored value, the currently measured temperature is displayed after t = 8 seconds. The display range for the outside temperature lies between T = -40 and +85 °C or between T = -40 and +185 °F.

If the instrument cluster receives implausible values or none at all for the coolant temperature, the display of the outside temperature is regulated as if the coolant temperature was T > 60 °C.

Function sequence for displaying the time 

The time is shown in the multifunction display of the instrument cluster or in the analog clock (A70/1) (model 205 up to 31.05.2016 or model 205 as of 01.06.2016 with code 246 (Analog clock)).

The time can either be entered manually in the system settings or is automatically updated via the received GPS (Global Positioning System) signals (with code 531 (COMAND APS) or code 522 (Audio 20 radio) with code 357 (Card navigation)).

The head unit (A26/17) transmits information on the time to the instrument cluster via the user interface CAN.

The instrument cluster synchronizes the displayed time with the information from the head unit and sends the current time to the front SAM control unit via user interface CAN, electronic ignition lock control unit and interior CAN. The front SAM control unit actuates the analog clock (model 205 up to 31.05.2016 or model 205 as of 01.06.2016 with code 246 (Analog clock)) via the instrument panel LIN (LIN 1).

Function sequence for scale illumination of instrument cluster 

The scale illumination is switched on when the instrument cluster is activated. The brightness is automatically adapted to the ambient brightness (day/night) by the instrument cluster.

When it is dark, the brightness can also be personalized by actuating the brightness control instrument illumination (S1r1) in the exterior lights switch (S1). The front SAM control unit reads in the signals from the instrument illumination brightness control directly and sends them via interior CAN, electronic ignition lock control unit and user interface CAN to the instrument cluster. Depending on these signals, the instrument cluster regulates the brightness of all display elements.

	Electrical function schematic of instrument cluster, comfort display		PE54.30-P-2056-97FBA
	Overview of system components, instrument cluster (IC) component description		GF54.30-P-9996RF