Wiper/Washer System Components
The wiper/washer system consists of the following electrical components:
• Windshield Wiper Relay
• Windshield Wiper Speed Control Relay
• Windshield Washer Pump Relay
• Rain Sensor (optional)
• Windshield Washer Fluid Pump
• Windshield Wiper Motor
• Window Wiper/Washer Switch
• Body Control Module (BCM)
Windshield Wiper System
The BCM determines the front wipe/wash system mode of operation by monitoring several signals from the front wipe/wash switch as
indicated in the wiper switch.
The front wipe/wash switch receives a reference ground signal from the BCM. Each input of the BCM provides a switched battery pull-up for
each front wiper/washer switch output signal it receives. All the BCM inputs are recognized as active when the wiper switch provides a path
to the referenced ground signal. The first signal received by the BCM is the result of 6 resistors in the front wiper switch configured as a
resistor ladder network. This signal is connected to a BCM analog to digital input. Depending on the function selected (High, Low,
Intermittent 1 to 5, Mist, Off), the front wiper control switch connects a different set of resistors into the circuit resulting in different
voltages appearing on the BCM A/D input. By monitoring this voltage, the BCM determines how to control the wiper motor On/Off Relay. It
should be noted that High, Low, and Mist all have the same value on this signal circuit. The second signal received from the front wiper
switch is active only when the front wiper switch is in the high speed wiper position. When the wiper switch is not in the high speed
position, the switch is open and the signal circuit is pulled to battery by the BCM. When the wiper switch is in the high speed position, the
switch pulls the circuit low. The BCM determines how to control the Wiper high/low speed relay from this input. The third signal received
from the front wiper switch is from the momentary windshield wash control switch. When the washer switch is not active the switch is open
and the signal circuit is pulled to battery by the BCM. When the washer switch is active, the switch pulls the circuit low. The BCM controls
the windshield wash and windshield wash activated wiper operation based on this input.
The BCM controls front wiper motor operation through two output signals and the monitoring of one input signal. The two outputs (one
high side drive, one low side drive) are used to control two external wiper motor relays: front wiper motor on/off relay: which provides the
wiper motor with battery power when it is activated by the high side drive signal (switched battery) from the BCM. When left deactivated,
the normally closed contacts provide a ground to the wiper motor. Wiper high/low speed relay: when activated by a low side drive signal
(ground) from the BCM, it switches the power supplied by the wiper motor's on/off relay to the motors high speed input. When left
deactivated, the normally closed contacts connect the power supplied by the wiper motor's on/off relay to the motor's low speed input. The
input used by the BCM is from the park switch located in the wiper motor assembly. When the wiper blades are not in the park position,
the wiper park switch is open and the circuit is pulled up to battery by the BCM. When the wiper blades are in the park position at the
bottom of the glass, the wiper park switch closes to ground pulling the park signal circuit low.
To initiate low speed operation, the BCM only energizes the front wiper motor on/off relay. This allows battery voltage from the wiper fuse
to be applied through the switched contacts of the wiper motor on/off relay, through the normally closed contacts of the wiper high/low
speed relay, to the low speed control circuit of the windshield wiper motor.
The BCM provides redundant circuitry which places battery power on its wiper motor on/off relay output with activation of its low assertion
high speed wiper switch input. The BCM shall be capable of doing this, even if the module has lost all microprocessor control. This
redundant circuit shall supply power while in the RUN and CRANK power modes. however; while in the CRANK power mode, the pass
through shall only be active if the BCM is NOT in a computer operating properly state.
To initiate high speed operation, the BCM energizes both the front wiper motor on/off relay and the wiper high/low speed relay. This allows
battery voltage from the wiper fuse to be applied through the switched contacts of the wiper motor on/off relay, through the switched
contacts of the wiper high/low speed relay, to the high speed control circuit of the windshield wiper motor.
In order to perform an accurate read of the park switch and to ensure the wipers will come to rest while still in the park position, parking
of the wipers only occurs while in a low speed wiper mode. This requires that if the wipers are performing a high speed wiper operation at
the time they are required to park, the BCM shall transition the Wipers to low speed by deactivating the wiper high/low relay before
attempting to park. In order to park the wipers, the BCM monitors the park circuit until the park switch pulls the park circuit to ground. At
this time, the BCM will immediately deactivate the wiper motor on/off relay. The relay contacts will switch back to their normally closed
position and will apply ground to the wiper motor power inputs through the normally closed contacts of the wiper high/low relay. This
deactivates and dynamically brakes the wiper motor in the park position. When the wiper switch is turned to the OFF position while the
wiper motor is somewhere in mid-cycle, the BCM will continue to operate the motor until the wipers reach the park position. If the BCM is
running the wiper motor and does not see a state transition of the park switch after 8 s, the wipers will stop immediately when the wiper
switch is turned to OFF. If the ignition is turned OFF while the wipers are in mid-cycle, the wipers will stop immediately, regardless of
position. The BCM will park the wipers next time the ignition is turned ON.
The windshield wiper system MIST operation is identical to LOW speed operation, except that the MIST switch is a press and release type
switch. When the wiper switch is moved to the MIST position and released, low speed wiper motor operation is started and will continue
until 1 cycle is complete. If the wiper switch is moved to the MIST position and held, the wiper motor will operate in the LOW speed mode
until the switch is released.
Windshield wiper intermittent operation is a low speed wiper motor function with a variable delay interval between the wiper motor cycles.
The duration of the delay is controlled by the front wiper control switch's intermittent 1 to intermittent 5 settings. The wiper operation is as
follows:
The BCM will initiate a single wipe by activating its front wiper ON/OFF relay output.
1.
At the completion of a single wipe, the BCM will park the wipers as described above.
2.
The BCM will then pause the wipers in their park position for the time duration associated with intermittent delay switch setting.
3.
When the delay time expires repeat Steps 1 and 3 until the system is turned off or taken out of intermittent mode. If the wiper
switch is moved from a longer delay interval to a shorter delay interval, the BCM will command an immediate wipe cycle and reset
the delay timer to the shorter delay interval.
4.
Intermittent wiper operation may be vehicle speed sensitive. When enabled, the speed compensated intermittent feature causes the
intermittent wiper delay intervals to become shorter as a function of increased speed. As vehicle speed is reduced the intervals will become
closer to the predetermined.
...
S e c tion 04
BODY SY
S T
E
M
S
Wipers and Washers
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CHEVROLET CRUZE BODY REPAIR MANUAL 2010
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