Sprinter 2500 V6-3.0L DSL Turbo (2008)
Instrument Cluster / Carrier: Description and Operation
Ambient Temperature Indicator
Description
DESCRIPTION
An ambient temperature indicator is standard equipment on all instrument clusters. The ambient temperature indication can be toggled with a digital
speedometer indication within the cluster multi-function indicator Liquid Crystal Display (LCD) or dot matrix display unit. These displays are soldered
onto the cluster electronic circuit board and are visible through a window located near the center of the instrument cluster, between the analog
speedometer and the tachometer.
The ambient temperature indication consists of a numeric value with a + (plus) or - (minus) prefix, and the unit of measure is identified with the
characters °C (Celsius) or °F (Fahrenheit) directly following the temperature indication.
The indications of the ambient temperature indicator are not visible when the display is not illuminated. On vehicles not equipped with the optional
steering wheel buttons, when illuminated the indications appear as dark characters and icons silhouetted against a lighted field. On vehicles equipped
with the optional steering wheel buttons, when illuminated the indications appear as light characters and icons silhouetted against a dark field. When the
exterior lighting is turned OFF, the display is illuminated at maximum brightness. When the exterior lighting is turned ON the display illumination level
can be adjusted in concert with the cluster general illumination lighting using the + (plus) and - (minus) multi-function indicator push buttons.
The ambient temperature indicator is serviced as a unit with the instrument cluster.
Operation
OPERATION
The ambient temperature indicator gives an indication to the vehicle operator of the outside air temperature. This indicator is controlled by the
instrument cluster microprocessor based upon cluster programming and electronic ambient temperature messages received by the cluster over the
Controller Area Network (CAN) data bus from the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM).
The ambient temperature indicator is completely controlled by the instrument cluster logic circuit, and that logic will allow this indicator to operate
whenever the cluster multi-function indicator display unit is active. Therefore, the ambient temperature indicator remains functional regardless of the
ignition switch position. The vehicle operator can choose to have a digital speedometer information displayed instead of the ambient temperature
indicator, but the digital speedometer and ambient temperature indicator cannot be displayed at the same time.
On vehicles without the optional steering wheel buttons, the digital speedometer or ambient temperature indicator display option is selected using the
multi-function indicator M (Mode) switch on the instrument cluster circuit board. This switch is actuated manually by depressing the push button that
extends through the left edge of the cluster lens outboard of the analog speedometer. Actuating this switch for more than one second will toggle the
display between the ambient temperature indicator and the digital speedometer modes. On vehicles with the optional steering wheel buttons, the digital
speedometer or ambient temperature indicator display option is selected using the multi-function indicator MENU switches on the steering wheel.
The ambient temperature sensor located below the front bumper is a Negative Temperature Coefficient (NTC) thermistor. The internal resistance of the
sensor is reduced as the ambient temperature rises. The BCM continually monitors the resistance through the sensor to determine the temperature value
to be displayed. The current value is displayed immediately after the display unit is activated. The display value will remain static regardless of decreases
in the sensor resistance (temperature rising) below vehicle speeds of 10 to 15 kilometers-per-hour (6 to 9 miles-per-hour). Decreases in the sensor
resistance above 15 kilometers-per-hour (9 miles-per-hour) and increases in the sensor resistance (temperature falling) regardless of vehicle speed are
displayed subject to a sixty second delay.
For proper diagnosis of the ambient temperature sensor and circuits, the BCM, the ElectroMechanical Instrument Cluster (EMIC) (also known as the
Cab Compartment Node/CCN or KOMBI), the CAN data bus or the electronic communication related to ambient temperature indicator operation, a
diagnostic scan tool is required. Refer to the appropriate diagnostic information.
