Volvo Penta D1-13 Workshop Manual page 18

30-2 Fault Tracing
a
LBN
5
MDI
P0008412
a Engine connector
b Coolant Temperature
16
Coolant temperature warning
Tachometer
The tachometer LCD screen will show a flashing cool-
ant temperature icon and the alarm buzzer sounds.
Alarm display
The coolant temperature indication flashes in the alarm
display + audible warning.
Circuit description
The coolant temperature sensor consists of a thermis-
tor. The property of a thermistor is that its resistance
b
changes non-linearly with temperature in the medium
1
it measures. Pin 5 in the engine interface connector at
the MDI supplies the thermistor with a reference volt-
age of +5 Volt. The sensor is connected to battery
negative via the engine. When the engine coolant is
cold, the sensor resistance is high and the MDI senses
a voltage close to the reference level. When the cool-
ant heats up, the resistance in the thermistor falls and
the voltage drop across the thermistor changes.
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