Display outside temperature, function - GF54.30-P-3019SKA
Model 171.4 as of 1.6.05
The outside temperature indicator in the lower multifunction display (A1p15) takes the following signals into consideration when indicating the temperature:
- Ambient temperature
- Vehicle speed
- Coolant temperature
- Engine running time
Displaying outside temperature
The instrument cluster (A1) processes the signals and activates the outside temperature indicator in the lower multifunction display (A1p15). The information is also placed on the Controller Area Network Class C bus (engine compartment) (CAN-C).
The dependency of the outside temperature indicator in the lower multifunction display (A1p15) on vehicle speed, engine running time and coolant temperature prevents too high an outside temperature being displayed when the vehicle is stationary or moving slowly.
The outside temperature indicator in the lower multifunction display (A1p15) will react differently depending on the coolant temperature and engine running time, whereby a drop in outside temperature is always shown.
Coolant temperature ≤ 60°C
At coolant temperatures ≤ 60°C, the current outside temperature appears when the instrument cluster (A1) is activated.
Coolant temperature ≥ 60°C
If the coolant temperature is ≥ 60°C, with "terminal 15 OFF" the outside temperature last measured is stored and displayed.
The outside temperature stored is displayed when the instrument cluster (A1) is activated. If the outside temperature measured drops below the stored value, the outside temperature currently measured is displayed after 8 seconds.
When driving the delay periods also depend on vehicle speed:
- At vehicle speeds between 20 and 45 km/h, increasing outside temperatures are displayed after a delay period of 3 minutes.
- At vehicle speeds of > 45 km/h increasing outside temperatures are displayed after a delay period of 1.5 minutes.
- When the vehicle speed drops below 20 km/h, the display only changes if the measured outside temperature drops.
Rising outside temperatures with engine off
If the outside temperature rises above the stored value with the engine off, the currently measured outside temperature is not shown in the lower multifunction display (A1p15) until 6 times the engine running time has elapsed. This is based on the previous engine running time.
Example
The preceding engine running time was 5 minutes. The delay period was therefore 6 _ 5 minutes. The current outside temperature is thus only displayed after 30 minutes. If the engine running time was > 10 minutes, a maximum of 10 minutes is considered for the calculation of the delay period. The maximum delay is thus 60 minutes.
The engine running time is calculated internally in the instrument cluster (A1) using the integral timer.
Reading in the required data for outside temperature:
- The outside temperature indicator temperature sensor (B14) changes its resistance according to the outside temperature. The outside temperature indicator temperature sensor (B14) is a negative temperature coefficient (NTC) resistor, i.e. the resistance decreases as the temperature increases.
- The NTC resistor of the outside temperature indicator temperature sensor (B14) is read in by the driver-side SAM control unit with fuse and relay module (N10/1).
- The driver-side SAM control unit with fuse and relay module (N10/1) converts the resistance value of the outside temperature display temperature sensor (B14) into a temperature value.
- This temperature value is placed on the Controller Area Network bus class B (interior) (CAN-B) by the driver-side SAM control unit with fuse and relay module (N10/1).
The instrument cluster (A1) processes these signals and activates the outside temperature indicator in the lower multifunction display (A1p15).
Reading in signals for vehicle speed:
- The rpm sensor, left front (L6/1), the rpm sensor, right front (L6/2), the rpm sensor, left rear (L6/3) and the rpm sensor, right rear (L6/4) are monitored by the ESP and BAS control unit (N47-5).
- The ESP and BAS control unit (N47-5) furnishes the signals from the rpm sensor, left front (L6/1), rpm sensor, right front (L6/2), rpm sensor, left rear (L6/3) and the rpm sensor, right rear (L6/4) on CAN-C.
- The instrument cluster (A1) receives these signals and uses them as the basis for calculating vehicle speed.
Reading in signals for coolant temperature:
- The coolant temperature sensor (B11/4) changes its resistance corresponding to coolant temperature. The coolant temperature sensor (B11/4) is an NTC resistor, i.e. the resistance decreases as the temperature increases.
- The resistance of the coolant temperature sensor (B11/4) is read in by the ME-SFI [ME] control unit (N3/10) and converted into a temperature value.
- The ME control unit (N3/10) passes this temperature on the engine compartment CAN.
The instrument cluster (A1) processes these signals and activates the coolant temperature gauge in the upper multifunction display (A1p13).
Changing over from degrees Celsius (°C) to degrees Fahrenheit (°F)
It is no longer possible to change from degrees Celsius (°C) to degrees Fahrenheit (°F) using the "Settings" function in the upper multifunction display (A1p13). Depending on the national version, degrees Celsius (°C) is changed over to degrees Fahrenheit (°F) by means of appropriate variant coding of the instrument cluster (A1) via the EIS [EZS] control unit (N73).
Range
The display range is -40 to +85°C or -40 to +185°F. The temperature is displayed in increments of 0.5°C or 1°F.
If the measured outside temperature exceeds the display range, the maximum display value is shown.
If the measured outside temperature drops below the display range, the minimum display value is shown.
| Instrument cluster (IC), location / task | GF54.30-P-3039SK |