Wipers and Washers - Operation

OPERATION

WIPER/WASHER SYSTEM





All wiper/washer system functions are initiated with the control knob on the end of the multifunction switch control stalk that extends from the left side of the steering column, just behind the steering wheel. Rotating the control knob on the end of the control stalk, selects the off, intermittent, auto (on models equipped with automatic wipers), low, or high front wiper system operating modes. In the intermittent mode, the control knob allows the vehicle operator to select from one of six intermittent wipe intervals. In the auto mode, the control knob allows the vehicle operator to select from one of six automatic wiper sensitivity levels. Pressing in on the end of the control stalk momentarily activates the Mist Wipe. Pressing it in all the way activates the windshield washers. In the auto mode, the sensitivity of the wipers is increased (less delay between wipes), the result is a corresponding acknowledgment wipe to let you know an adjustment has been made to the system. The multifunction switch provides hard-wired-resistor multiplexed inputs to the Steering Column Control Module (SCCM), for all of the wiper/washer system functions. The SCCM then sends electronic messages to the Front Control Module (FCM) over the Controller Area Network (CAN) data bus requesting the appropriate front wiper/washer system operating modes.

All wiper/washer system operation is controlled by the FCM logic circuits. That logic will only allows these systems to operate when the ignition switch is in the accessory or on positions. Battery current is directed from a B(+) fuse in the Integrated Power Module (IPM) to the wiper on/off relay, and the wiper high/low relay in the Power Distribution Center (PDC) through a fused B(+) circuit. The FCM uses low side drivers to control wiper system operation by energizing or de-energizing the wiper high/low and wiper on/off relays. The FCM uses both high side and low side drivers to control the operation of the washer pump/motor unit. The multifunction switch circuitry receives a clean ground output from the SCCM on a multifunction switch return circuit, then provides resistor multiplexed inputs to the SCCM on an intermittent wipe mux circuit to indicate the selected wiper system mode and on a wash/beam select mux circuit to indicate the selected washer system mode.

CONTINUOUS WIPE MODE

When the low position of the multifunction switch is selected, the SCCM sends an electronic wiper switch low message to the FCM, the FCM then energizes the wiper on/off relay. This directs battery current to the low speed brush of the wiper motor through the normally open contacts of the energized wiper on/off relay and the normally closed contacts of the de-energized wiper high/low relay causing the wipers to cycle at low speed.

When the high position of the control knob is selected, the SCCM sends an electronic wiper switch high message to the FCM, the FCM then energizes both the wiper on/off and the wiper high/low relays. This directs battery current to the height speed brush of the wiper motor through the normally open contacts of the energized wiper on/off relay and the normally open contacts of the energized wiper high/low relay, causing the wipers to cycle at high speed.

When the off position of control knob is selected, the SCCM sends an electronic wiper switch off message to the FCM. If the wiper motor was operating at high speed, the FCM immediately de-energizes the wiper high/low relay causing the wiper motor to return to low speed operation, causing one of two events to occur. The event that occurs depends on the position of the wiper blades on the windshield at the moment that the control knob off position is selected.

If the wiper blades are in the down position on the windshield when the off position is selected, the park switch that is integral to the wiper motor is closed to ground and provides a hard wired park switch sense input to the FCM. The FCM then de-energizes the wiper on/off relay and the wiper motor ceases to operate. If the wiper blades are not in the down position on the windshield at the moment the off position is selected, the park switch is an open circuit and the FCM keeps the wiper on/off relay energized, causing the wiper motor to continue running at low speed until the wiper blades are in the down position on the windshield and the park switch input to the FCM is again closed to ground.

HEADLAMPS ON WITH WIPERS MODE

The CCN provides an automatic headlamps on with wipers feature for models equipped with automatic headlamps. This is a customer programmable feature. If this feature is enabled, the headlamps turn on automatically whenever the windshield wipers are turned on, and turn off automatically when the wipers are turned off. If this feature is enabled, when the automatic wiper mode is selected, the headlamps turn on automatically only after the wipers complete a minimum of five automatic wipe cycles within about 60 seconds.The headlamps turn off automatically after four minutes elapse without any wipe cycles.

INTERMITTENT WIPE MODE

When the control knob of the multifunction switch control knob is moved to one of the intermittent interval positions, the SCCM sends an electronic wiper switch delay message to the FCM, then the FCM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon the selected delay interval input. The FCM monitors the changing state of the wiper motor park switch through a hardwired park switch sense input. This input allows the FCM to determine the proper intervals at which to energize and de-energize the wiper on/off relay and to operate the wiper motor intermittently for one low speed cycle at a time.

The FCM logic is also programmed to provide vehicle speed sensitivity to the selected intermittent wipe delay intervals. In order to provide this feature the FCM monitors electronic vehicle speed messages from the Powertrain Control Module (PCM) and doubles the selected delay interval whenever the vehicle speed is approximately 16 km/h (10 mph) or less.

PULSE WIPE MODE

When the control knob of the multifunction switch control stalk is pressed to the momentary pulse wipe position for less than one-half second, the SCCM sends an electronic switch message to the FCM, the FCM then energizes the wiper on/off relay for one complete wipe cycle. The FCM de-energizes the relay when the state of the park switch sense changes to ground, parking the wiper blades near the base of the windshield.

WASH MODE

When the control knob of the multifunction switch control stalk is pressed to the momentary wash position for more than one-half second, the SCCM sends an electronic washer switch message to the FCM, the FCM then directs battery current and ground to the washer pump/motor unit. This causes the washer pump/motor unit to be energized for as long as the Wash switch is held closed, up to about 10 seconds, and to de-energize when the front Wash switch is released.

When the control knob is pressed to the momentary wash position while the wiper system is operating in one of the intermittent interval positions, the washer pump/motor operation is the same. However, the FCM also energizes the wiper on/off relay to override the selected delay interval and operate the wiper motor in a continuous low speed mode for as long as the control knob is held pressed, then de-energizes the relay and reverts to the selected delay mode interval several wipe cycles after the control knob is released. If the control knob is held pressed for more than 10 seconds, the FCM suspends washer pump/motor operation until the knob is released, then cycled back to the wash position, if so desired.

The headlamp washer system (if equipped) uses a separate high pressure pump attached to the windshield washer reservoir. The headlamp washer pump feeds then nozzles mounted in the front fascia of the vehicle. The nozzle bodies spray the headlamps with high pressure washer solvent when the system is activated.

To activate the headlamp washers, turn the headlamps on and press the windshield washer control knob. This operates the windshield washers and directs two, timed, high pressure sprays onto the headlamp lens.

WIPE-AFTER-WASH MODE

When the control knob of the multifunction switch control stalk is pressed to the momentary wash position for more than one-half second while the wiper system is not operating, the instrument cluster sends an electronic washer switch message to the FCM, the FCM then directs battery current and ground to the washer pump/motor unit and energizes the wiper on/off relay. This will causes the washer pump/motor unit to be energized and operate the wiper motor in a continuous low speed mode for as long as the wash switch is held closed, up to about 10 seconds. When the control knob is released, the FCM de-energizes the washer pump/motor unit, but allows the wiper motor to operate for several additional wipe cycles before it de-energizes the wiper on/off relay and parks the wiper blades near the base of the windshield.

If the control knob is held pressed for more than 30 seconds, the FCM suspends washer pump/motor operation until the knob is released, then cycled back to the wash position. However, the wipers continue to operate for as long as the wash switch is held closed. The FCM monitors the changing state of the wiper motor park switch through a hardwired wiper park switch sense circuit input. This input allows the FCM to count the number of wipe cycles that occur after the wash switch is released, and to determine the proper interval at which to de-energize the wiper on/off relay to complete the wipe-after-wash mode cycle.