300E 4MATIC (124.230) L6-3.0L (103.985) (1990)
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Temperature Sensor (Gauge): Description and Operation
Temperature Sensor Location
PURPOSE
The coolant temperature gauge sensor is a multi-function sensor. Along with providing the ground circuit for the temperature gauge, it activates the
auxiliary fan via the ACC control unit and the high speed relay, and deactivates the compressor clutch via the compressor cut-out control unit, in order to
prevent engine overheat. In addition, it influences the the blower speed via the ACC control unit.
LOCATION
The coolant temperature sensor is located at the intake side of the cylinder head.
OPERATION
The coolant temperature sensor activates the auxiliary fan (high speed) via the ACC control unit at approx. 224°F (107°C). As the temperature drops
below approx. 212°F (100°C) fan operation discontinues.
If the ambient temperature is greater than 77°F (25°C), the auxiliary fan (high speed) will also be activated if:
^
There is an open circuit in the coolant temperature sensor.
^
The 2-pole connector on the coolant temperature sensor is disconnected.
When the coolant temperature reaches 242°F (117°C), the operating time of the compressor will be reduced by 50%, cycling 20 seconds "OFF" and 20
seconds "ON" (stage 1 cycling). When the coolant temperature falls to 237°F (114°C), the compressor will resume normal operation.
At a coolant temperature of 248°F (120°C), the compressor will be switched "OFF" completely (stage 2 "OFF"). When the coolant temperature falls to
242°F (117°C), the compressor will operate as in stage 1 cycling.
