Volt

Wiper/Washer System Description and Operation

The wiper/washer system consists of the following electrical components:

On Wiper System Smart equipped vehicles, the body control module (BCM) will command front wiper operations via local interconnect network (LIN) serial data communications instead of via ON/OFF and HIGH/LOW Wiper Motor Relay Drive Outputs. In front wiper systems using the Wiper System Smart - Single configuration, the Driver's side and Passenger's side Wiper Arm are connected by a mechanical linkage with a single integrated Front Wiper Motor/Controller operating them. The Front Wiper Motor/Controller contains the necessary electronics, motor, and position sensors to execute front wiper commands from the Body Control Module. These internal electronics are integrated into the cover of the wiper motor gear housing and are not considered a serviceable item. The Front Wiper Motor/Controller wipes the front windscreen by controlling the up and down wiper arm movement by the use of a reversing motor and an internal position sensor. The sensor keeps track of the gear wheel position and when the Controller determines that the wiper arms are at a position to reverse direction, it reverses the motor supply voltage by use of its internal motor control circuitry. The interface between the BCM and the Front Wiper Motor/Controller utilises a Master/Slave configuration using a LIN serial data system for communication. The BCM is designated as the master, and the Front Wiper Motor/Controller is configured as the slave. As the System Master, the BCM uses the LIN communication bus to command Front Wiper operation, and communicate vehicle information to the Wiper Motor controller. The Front Wiper Motor/Controller provides system status and diagnostic information to the BCM for diagnostic reporting and operational purposes. The Body Control Module (BCM) also provides a hardwired redundant output that switches Battery power to the Wiper Motor upon activation of its low assertion High Speed Wiper Switch input. The BCM will do this, even if the module has lost all microprocessor control. The Front Wiper Motor/Controller gives priority to its LIN input over this Redundant Control Input, however, in the event that LIN communications are lost between the BCM and the Front Wiper Motor/Controller this redundant signal is used to command the required fail-soft wiper actions including Power Mode. While under Redundant Input control the Front Wiper Motor/Controller shall provide Continuous Low Speed Wiper operation when the input is Active, and will park the Wipers and go to Low Power Mode when the Redundant Input is Inactive.

While the Front Wiper Switch is either held in the MIST position (momentary contact switch) or is in its LOW position (latching switch), the BCM provides continuous Low Speed Wiper operation by commanding uninterrupted Low Speed Wiper operation by setting the transmitted LIN signal to Low Speed Wipe.

The BCM shall command the Wiper System Smart to perform Intermittent Wipes as follows:

1. Perform one immediate wipe by issuing a LIN signal set to Low Wipes. The Front Wiper Motor/Controller shall initiate Low Speed Wiper Operation and send a LIN signal back set to Low Wiping.
2. Upon the wipers leaving their PARKED position, the Front Wiper Motor/Controller shall send a LIN signal indicating the wipers are no longer in park.
3. Upon receipt of the Wiper out of Park LIN signal, the BCM shall transition the Front Wiper Command LIN signal to Park. While the wiper system smart is in the process of moving the wipers to their parked position, it shall set the value of its Wiper Front Status LIN signal to Parking.
4. The current wipe cycle will be completed and the wipers parked. Upon parking the wipers, the wiper system smart sends the Wiper Front Status LIN signal set to Parked.
5. Upon the transition of the LIN signal from Parking to Parked, the BCM pauses the Wipers in their Park Position for the time duration associated with the current intermittent delay interval switch setting and repeats the process

As called out above, the wipe delay interval is a function of the INTERMITTENT Delay Interval Switch setting. When enabled, the Intermittent with Speed feature affects each of the 5 normal Intermittent Delay Intervals as a function of vehicle Speed. The Delay Intervals shall be biased to a shorter delay period with faster vehicle speeds and to a longer delay period with a slower vehicle speed.

The BCM controls the windscreen wash operation and windscreen wash activated wiper operation. When the BCM detects the activation of the momentary windscreen wash control switch, it activates its washer pump relay drive output which supplies battery power to the coil of the washer pump relay. This energises the relay, which switches battery power to the pump motor. The BCM will also activate continuous low speed windscreen wipes as described above. Upon deactivation of the windscreen wash control switch, the wiper control module (BCM) shall deactivate the wash motor and will also park the wiper motor as described above unless the drip wipe feature is enabled. On some vehicles the drip wipe feature will be enabled and cause the system to provide additional wiping of the windscreen after the switch has been released and fluid is no longer being applied. The front wash feature may attempt to detect a stuck switch. When enabled, activation of the wash feature shall be limited to 10 seconds.

On vehicles with the Rear Wash feature a single reversing wash motor may be utilised for both the front and rear wash operation. In this system the wash motor is operated in one direction to spray fluid on the front windscreen and then operated in the reverse direction to spray fluid on the rear window. The BCM Controls the reversing wash motor through two High Side Drive outputs. One controls the Front Wiper Motor Relay and one controls the Rear Wiper Relay.