31
Superior
Technology
Coolant temperature sender
The coolant temperature sender is located on the
connection coupling for the coolant above the
coolant pump.
Its signal serves as a variable for determining the
engine temperature and for detecting whether
preheating, post-heating, standby heating or
increased idle speed is required when the engine
is cold (90 sec).
The signal is additionally used in the event of
engine overheating to reduce the power output.
Functional description
The coolant temperature sender features an NTC
bead. An NTC (
N
egative
T
emperature
C
oefficient) changes its resistance corresponding
to temperature. When the temperature increases
the resistance value drops. When the
temperature drops the resistance values
increases.
The engine control unit can detect the current
engine temperature from this resistance value.
Substitute function
If the engine control unit receives no signal from
the coolant temperature sender, a fixed value
stored in the engine control unit is used as the
substitute signal.
Effect
The MDC control unit receives no engine
temperature value from the coolant temperature
sender.
Engine electronic systems
MSSP_001_023
Summary of Contents for SDI 55-5
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