GF54.30-P-3019QO Display Outside Temperature, Function

GF54.30-P-3019QO Display Outside Temperature, Function

Component Identification:

Function requirements
The outside temperature indicator in the multifunction display (A1p13) takes into account the following data to display the temperature value:
^ Outside temperature value
^ Vehicle speed signal
^ Coolant temperature
^ Engine running time

Displaying outside temperature
The instrument cluster (A1) processes this data and actuates the display of the temperature value accordingly. Due to the dependency of the outside temperature indicator in the multifunctional display (A1p13) on vehicle speed, engine running time and coolant temperature when the vehicle is stationary or driving slowly the system prevents too high a temperature being displayed as can be caused by radiated engine heat for example. The display behaves differently according to the coolant temperature and the engine running time.

Coolant temperature < 60 °C
When the instrument cluster (A1) is activated the current outside temperature value is always.

Coolant temperature ≥60 °C
For circuit 15C the temperature value last measured is stored and displayed for a maximum of 60 minutes.
When the instrument cluster (A1) is activated the stored temperature value is displayed.
If the measured outside temperature falls below the stored value, the current measured temperature is displayed after 8 seconds. If the engine is off, the current outside temperature is displayed after six times the engine running time. This is based on the previous engine running time.

Display example of outside temperature
The preceding engine running time was 5 minutes. The delay time is then 6 X 5 minutes. The current temperature is thus only displayed after 30 minutes.
If the engine running time was more than 10 minutes, a maximum of 10 minutes is taken into account when calculating the delay time. The maximum delay is thus 60 minutes.
When the vehicle is moving, the delay periods depend on the vehicle speed. At speeds > 45 km/h rising outside temperatures are displayed after a delay period of 1.5 minutes.
At speeds of 20 to 45 km/h rising outside temperatures are displayed after a delay period of 3 minutes.
If the speed, coming from a higher speed, drops below 20 km/h, the display only changes when the measured value drops.

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.

Changeover from degrees Celsius (°C) to degrees Fahrenheit (°F)
The changeover from degrees Celsius (°C) to degrees Fahrenheit (°F) is no longer possible via the "Settings" function in the multifunction display (A1p13). Depending on the national version the changeover from degrees Celsius (°C) to degrees Fahrenheit (°F) takes place via the respective variant coding of the instrument cluster (A1) via the EIS [EZS] control unit (N73).

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, as a result the NTC-resistance decreases as the temperature increases.

The resistance value of the outside temperature indicator (B14) is read by the front SAM control unit with fuse and relay module (N10/1). The front SAM control unit with fuse and relay module (N10/1) converts the resistance value from the outside temperature indicator 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 front SAM control unit with fuse and relay module (N10/1).

Vehicle speed signal
The signals from the following speed sensors are read by the ESP and BAS control unit (N47-5):
^ Left front rpm sensor (L6/1)
^ Right front rpm sensor (L6/2)
^ Left rear rpm sensor (L6/3)
^ Right rear rpm sensor (L6/4)

The ESP and BAS control unit (N47-5) places the 4 wheel speed signals on CAN B via the front SAM control unit with fuse and relay module (N10/1).
The instrument cluster (A1) uses these to calculate the speed.

Coolant temperature
The coolant temperature sensor (B11/4) changes its resistance corresponding to coolant temperature. The coolant temperature sensor (B11/4) incorporates an NTC resistor in which resistance decreases as temperature rises.
The resistance value of the coolant temperature sensor (B11/4) is read via the CDI control unit (N3/9) or ME-SFI [ME] control unit (N3/10).
The CDI control unit (N3/9) or ME-SFI [ME] control unit (N3/10) converts the resistance value of the coolant temperature sensor (B11/4) into a temperature value.
This temperature value is placed on the Controller Area Network bus Class C (engine compartment) by the ME-SFI [ME] control unit (N3/10).

Engine running time
The engine running time is calculated internally in the instrument cluster (A1) using the integral timer. The instrument cluster (A1) processes this data and actuates the display of the temperature value accordingly.

Notes on diagnosis
If the display of temperature value indicates the lower temperature value -40 °C or -40 °F when the outside temperature is obviously higher, then there may be a break in the outside temperature indicator temperature sensor (B14) or an open circuit. If the display of temperature indicates the highest temperature value +85 °C or 185 °F when the outside temperature is obviously lower, then there may be a short circuit in the outside temperature indicator temperature sensor (B14) or in the line.

If the coolant temperature sensor (B11/4) and no valid coolant temperature values are passed on from CAN-C, the processing changes into the area for coolant temperature ≥60 °C.