DAF CF65, CF75, CF85 Series . Manual — part 497
5
CF65/75/85 series ≥0E621376
Description of components
COMPONENTS
2-3
Inspection
The duty cycle signal (square wave voltage) can
be checked using a multimeter that is set to the
DC voltage or duty cycle range or using a
scopemeter.
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COMPONENTS
Description of components
CF65/75/85 series ≥0E621376
2-4
2.3 TEMPERATURE SENSORS
The vehicle has a number of temperature
sensors, such as:
-
coolant temperature sensor
-
inlet air temperature sensor
-
fuel temperature sensor
-
ambient air temperature sensor
These sensors are temperature-sensitive
resistors.
Large changes in the resistance of these
sensors are perceptible when the temperature
rises or drops.
There are two types of temperature sensor:
-
NTC resistor (Negative Temperature
Coefficient).
-
PTC resistor (Positive Temperature
Coefficient).
NTC resistor
In an NTC resistor, the resistance value reduces
when the temperature rises.
Application:
-
measuring coolant temperature.
PTC resistor
In a PTC resistor, the resistance value increases
when the temperature rises.
In contrast to the NTC resistor, there will be a
large change in resistance within a small
temperature range in the PTC resistor.
Application:
-
measuring air temperature when cab heater
is on
W 5 01 010
W 5 01 011
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5
CF65/75/85 series ≥0E621376
Description of components
COMPONENTS
2-5
Inspection
The temperature sensors can be checked using
a multimeter that is set to the resistance range.
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5
COMPONENTS
Description of components
CF65/75/85 series ≥0E621376
2-6
2.4 FLUID LEVEL SENSORS
The vehicle has a number of fluid level sensors,
such as:
-
cooling system fluid level sensor
-
engine oil level sensor
Coolant level sensor
The coolant level sensor consists of two
microswitches (reed switches), connected in
parallel with two resistors.
These microswitches are influenced by a
magnetic field positioned outside the sensor.
If the coolant level drops, the microswitches will
be closed by a float fitted with a fixed magnet.
The “alarm switch” detects that the coolant level
is too low and short circuits the parallel switched
resistor.
The “daily inspection” switch detects that the
coolant needs to be topped up and short circuits
the parallel switched resistor.
The VIC uses the resistance value to detect the
status of the microswitches.
As a result the instrument display is activated by
the VIC.
Note:
The VIC will only send a message to the
instruments display during the startup phase if
the “daily inspection” switch is closed during the
startup phase.
Engine oil level sensor
The operation of the engine oil level sensor is
based on a resistance measurement.
When the contact is switched on, a current is
sent through the sensor from the VIC control
unit for a specific period of time.
Applying this current briefly in this way ensures
that the sensor is properly warmed up.
When the level is being measured the
resistance value is influenced by the quantity of
oil in the sump.
E501433
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E501434
E501146
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