RAM 1500 Truck 4WD V8-5.7L VIN D (2005)
The oil temperature gauge cannot be repaired or adjusted and, if damaged or faulty, it must be replaced. The gauge illumination LED unit is not available
for service replacement and, if damaged or faulty, the entire gauge must be replaced.
The oil temperature gauge gives an indication to the vehicle operator of the engine oil temperature. This gauge is controlled by its own internal electronic
circuit board based upon a hard wired input received by the gauge from an oil temperature sensor (4) installed in a tapped hole that penetrates an oil
passage on the right side of the engine block (2) just behind the oil pressure sensor (3).
The oil temperature sensor is a Negative Temperature Coefficient (NTC) thermistor that changes its internal resistance with changes in temperature. The
sensor has two terminals. One terminal receives a hard wired ground path through a take out and connector of the engine wire harness (1), and the second
terminal provides a variable output to the gauge through the same take out and connector. As the oil temperature increases the resistance of the sensor
decreases, and as the oil temperature decreases the resistance of the sensor increases.
The oil temperature gauge is an air core magnetic unit. The gauge pigtail wire and connector provides the gauge electronic circuit board with a hard
wired ground path, battery current through a fused ignition switch output (run-start) circuit, a Pulse Width Modulated (PWM) panel lamps dimmer input
from the instrument cluster for general illumination, and the input from the oil temperature sensor. This gauge is only operational when the ignition
switch is in the On or Start positions. The gauge electronic circuit board reads the input from the oil temperature sensor, then provides linear positioning
of the gauge needle on the gauge scale based upon that input. The gauge electronics will move the gauge needle back to the low end of the scale after the
ignition switch is turned to the Off position.
The oil temperature gauge and the oil temperature sensor may be diagnosed using conventional diagnostic tools and methods.
