Comfort displays, function - GF54.30-P-3043GM

MODEL 164.1 as of model year 2009 

MODEL 164.8, 251.0/1 as of model year 2009 

Function requirements, general 

• Instrument cluster (A1) activated

Comfort displays in general 

The comfort displays function provides a fast overview of supplemental information, which however is not required for operation of the vehicle.

The comfort display function includes the following subfunctions:

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

Function sequence for displaying outside temperature 

The outside temperature is recorded by the outside temperature indicator temperature sensor (B14).

The AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or the comfort AAC [K-KLA] control and operating unit (N22/7) (with code (581) Comfort automatic air conditioning) reads in the signals of the outside temperature indicator temperature sensor directly, calculates from these the outside temperature and transmits it over the interior CAN (CAN B) to the instrument cluster.

The following parameters must also be taken into account to determine a correct value of outside temperature:

• 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 ESP control unit (N47-5) (except model 164.195) or the regenerative braking system control unit (N30/6) (on model 164.195) sends information about wheel speeds to the instrument cluster via engine compartment CAN (CAN C).

The CDI control unit (N3/9) (with diesel engine) or the ME-SFI [ME] control unit (N3/10) (with gasoline engine) sends information on the coolant temperature via the engine compartment CAN to the instrument cluster.

The coolant temperature values have an influence on the outside temperature indicator as follows:

• Coolant temperature T < 60 °C:

  The current outside temperature value is always shown.

• Coolant temperature T > 60 °C and signal "Engine running" set:

  At vehicle speeds of v < 20 km/h (12 mph) (with vehicle deceleration), the outside temperature display is only changed if the measured outside temperature value drops. At vehicle speeds of v = 20 and 45 km/h, rising outside temperatures are displayed after a delay period of t = 3 min.

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

• Coolant temperature T > 60 °C and signal "Engine running" 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 the outside temperature display value is not permitted during this delay period.

The CDI control unit or the ME-SFI [ME] control unit sends the signal "Engine running" via the engine compartment CAN to the instrument cluster.

With circuit 15 OFF, the last measured temperature value is stored and then displayed when the circuit is reactivated. The circuit 15 status is sent by the EZS control unit (N73) over the interior CAN to the instrument cluster.

The display range for the outside temperature is between T = -40 and +85 °C or between T = -40 and +185 °F. The display appears in the lower range of the multifunction display (A1p13).

If the instrument cluster receives implausible values or no values at all for the coolant temperature, the display of outside temperature is controlled as if the coolant temperature were T > 60 °C.

Function sequence for displaying the time 

The time is displayed analog in the electronic clock (A1p6). In vehicles without code (511) Audio 50 APS incl. DVD changer and without code (525) MB Audio 50 APS radio and without code (512) COMAND APS incl. DVD changer and without code (527) COMAND APS with single DVD drive (with navigation), the time can only be adjusted manually using the left multifunction steering wheel button group (S110) and the right multifunction steering wheel button group (S111).

The steering wheel electronics (N135) read in the control signals of the multifunction steering wheel button groups directly and transmit them over the steering LIN (LIN E1), steering column tube module (N80) and engine compartment CAN to the instrument cluster.

For vehicles with code (511) Audio 50 APS incl. DVD changer or code (525) MB Audio 50 APS radio or code (512) COMAND APS incl. DVD changer or code (527) COMAND APS with single DVD drive (with navigation), the time is automatically synchronized with the radio and navigation unit (A2/56) or the COMAND operating, display and controller unit (A40/3) by the received global positioning system (GPS) signal. Manual adjustment of the time is not possible.

The radio and navigation unit or the COMAND operating, display and controller unit sends a time synchronization signal via the interior CAN to the instrument cluster.

Function sequence for illumination of instrument cluster 

The illumination is switched on automatically when the instrument cluster is activated.

If the instrument cluster is activated by opening the driver door, the illumination is switched off again after t = 30 s. If an active warning is displayed, the run-on time is extended by an additional t = 2 min. The brightness is automatically adapted to the interior brightness conditions by the brightness sensor (A1b1).

Depending on the light falling on the brightness sensor, the instrument cluster automatically regulates the lighting in a range between 80 % to 100 % of the maximum brightness. The brightness can also be changed individually by pressing the instrument and switch and controls illumination button, bright (A1s4) or the instrument and switch and controls illumination button, dark (A1s5), provided that the exterior lights are switched on.

If, during active auto on/off headlamps, the rain/light sensor (B38/2) transmits the "Darkness detected" status, the instrument cluster switches automatically to night mode. The brightness is then approx. 50 % of the day mode and it can also be adjusted using the instrument and pushbutton unit illumination switch.

If the rain/light sensor transmits the "Day" status, then the instrument cluster regulates the lighting in a range of between 80 % to 100 % of the maximum brightness. Manual readjustment via the instrument and switch and controls illumination button is not possible here.

The overhead control panel control unit (N70) reads in the signals of the rain/light sensor directly and transmits them over the interior CAN to the instrument cluster. The status of the rotary light switch (S1) is read in over the instrument panel LIN (LIN 1) by the upper control panel control unit (N72/1), which then sends it over interior CAN to the instrument cluster.

Electrical function schematic of instrument cluster, comfort display	MODEL 164.1 (except 164.195) as of model year 2009 MODEL 164.8 as of model year 2009	PE54.30-P-2056-97MAA
	MODEL 164.195 as of model year 2009	PE54.30-P-2056-97MAB
	MODEL 251.0/1 as of model year 2009	PE54.30-P-2056-97RAA
Overview of system components, instrument cluster (IC) component description		GF54.30-P-9996GM