GF54.30-D-3019H Display Outside Temperature, Function

GF54.30-D-3019H Display Outside Temperature, Function

- with CODE (J65) Outside temperature indicator







Shown with engine 272 and with code (JK3) High-end instrument cluster standard with speedometer in km
A1 Instrument cluster
B11/4 Coolant temperature sensor
B14 Outside air temperature sensor
L6/1 Left front rpm sensor
L6/2 Right front rpm sensor
L6/3 Left rear rpm sensor
L6/4 right rear rpm sensor
N3/23 ME control unit
N10 SAM control unit
N30/4 ESP control unit

The outside temperature indicator takes account of the following data to display the temperature value:
- The outside temperature reading
- The vehicle speed signal
- The coolant temperature
- the engine running time

Displaying outside temperature
The instrument cluster processes this data and actuates the outside temperature indicator in the display (A1p1) accordingly.
The dependency of the temperature shown in the outside temperature indicator on the vehicle speed, the engine running time and the coolant temperature prevents an excessively high temperature being displayed when the vehicle is stationary or moving slowly, such as might occur due to heat radiating from the engine, for example.
The display varies according to the coolant temperature and the engine running time.

Coolant temperature < 60 °C
When the coolant temperature is < 60 °C, the current outside temperature value is always displayed when the instrument cluster is activated.

Coolant temperature ≥ 60 °C
If the coolant temperature is ≥ 60 °C, the temperature value last measured is stored and displayed when the status changes from "circuit 15 ON" to "circuit 15 OFF".
When the instrument cluster is activated, the stored temperature is always displayed. If the outside temperature measured drops below the stored value, the temperature currently measured is displayed after a delay period of t = 8 seconds.

When the vehicle is being driven, the delay periods also depend on the vehicle speed:
- At speeds of 20 to 45 km/h rising outside temperature are displayed after a delay period of t = 3 minutes.
- At speeds > 45 km/h, rising outside temperatures are displayed after a delay period of t = 90 seconds.
- With a reduction in speed < 20 km/h the display is only changed when the measured outside temperature value drops.

If the instrument cluster does not receive a valid coolant temperature from the Controller Area Network bus class C (engine compartment) (CAN-C), the outside temperature is determined in the same way as for a coolant temperature ≥ 60 °C.

Rising outside temperature with engine OFF following engine running period
If the outside temperature rises above the stored value with engine OFF, the currently measured outside temperature is not shown in the outside temperature indicator of the display until a period corresponding to 6 times the engine running time (or max. one hour) has elapsed. This is based on the previous engine running time. If the coolant temperature drops below 60 °C, the delay period counter is reset immediately and rising temperatures are shown in the outside temperature indicator of the display.

Example: Delay period for outside temperature indicator
The preceding engine running time was t = 5 minutes. The delay period is then 6x5 minutes. The current temperature is thus only displayed after t = 30 minutes. If the engine running time was more than t = 10 minutes, a maximum of t = 10 minutes is taken into account for calculating the delay period. As a result the maximum delay is t = 60 minutes.

Information flow and networking
Reading in the data for the coolant temperature value:
- The coolant temperature sensor changes its resistance corresponding to the coolant temperature. The sensor has a negative temperature coefficient (NTC) resistance, i.e. the resistance reduces as temperature increases.
- The resistance of the coolant temperature sensor is read in by the ME-SFI [ME] control unit (N3/23), the CDI control unit (N3/20) or the CDI control unit (N3/21) and converted into a temperature value.
- This value is placed on CAN-C by the ME-SFI [ME] control unit (N3/23), the CDI control unit (N3/20) or the CDI control unit (N3/21).
- The instrument cluster receives these signals via CAN-C.

Reading in the data for the vehicle speed signal:
- The left front rpm sensor, right front rpm sensor, left rear rpm sensor and right rear rpm sensor are read in by the ESP control unit.
- The ESP control unit places the signals from the left front rpm sensor, right front rpm sensor, left rear rpm sensor and right rear rpm sensor on CAN-C.
- The instrument cluster receives these signals via CAN-C and uses them to determine the speed of the vehicle.

Reading in the required data for outside temperature:
- The outside air temperature sensor changes its resistance according to the outside temperature. The sensor has an NTC resistance, i.e. the resistance reduces as temperature increases.
- The resistance of the outside air temperature sensor is read in discretely by the SAM control unit and then placed on CAN-B.
- The instrument cluster converts the resistance value of the outside air temperature sensor into a temperature value.

The engine running time is determined internally in the instrument cluster using the integrated timer and stored.
The instrument cluster processes this data and actuates the outside temperature indicator in the display accordingly.

Switching from degrees Celsius (°C) to degrees Fahrenheit
(°F) with code (JK3) High-end instrument cluster standard with speedometer in km
Degrees Celsius (°C) is switched over to degrees Fahrenheit (°F) using the "Settings" function in the display.

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 outside temperature measured exceeds the display range the maximum display value of the display range is shown.
If the outside temperature measured drops below the display range, the minimum display value of the display range is shown.

Notes on diagnosis
If the display indicates the minimum temperature of -40 °C or -40 °F although the actual outside temperature is obviously higher, this could indicate a defective sensor or an open circuit.
If the display indicates the maximum temperature value 85 °C or 185 °F although the actual outside temperature is obviously lower, this could indicate a short circuit in the outside air temperature sensor or in the line.