Front

FRONT





The front wiper and washer system is designed to provide the vehicle operator with a convenient, safe, and reliable means of maintaining visibility through the windshield glass. The various components of this system are designed to convert electrical energy produced by the vehicle electrical system into the mechanical action of the wiper blades to wipe the outside surface of the glass, as well as into the hydraulic action of the washer system to apply washer fluid stored in an on-board reservoir to the area of the glass to be wiped. When combined, these components provide the means to effectively maintain clear visibility for the vehicle operator by removing excess accumulations of rain, snow, bugs, mud or other minor debris from the outer surface of the windshield glass that might be encountered while driving the vehicle under numerous types of inclement operating conditions.

The vehicle operator initiates all front and rear wiper and washer system functions with the control stalk of the right (wiper) multi-function switch that extends from the right side of the steering column, just below the steering wheel. Moving the control stalk to a detent position selects the OFF, DELAY (or INTERMITTENT), LOW or HIGH front wiper system operating modes. Pulling the control stalk to a momentary rearward position actuates the front washer system switch, which selects the front WASH mode and dispenses washer fluid in the wipe pattern on the windshield for as long as the switch is held closed. Lifting the control stalk to a momentary upward position selects the MIST (or PULSE) mode, which cycles the wiper blades for as long as the switch is held closed then completes the current wipe cycle and parks the blades at the base of the windshield after the switch is released.

The right multi-function switch provides hard wired analog and resistor multiplexed inputs to the Body Control Module (BCM) for all of the wiper and washer system functions. The BCM then provides the appropriate hard wired control outputs to energize or de-energize the wiper and washer relays soldered onto its printed circuit board. The relays control the flow of battery current to the front wiper motor and washer pump motor, invoking the requested wiper and washer system operating modes. Front wiper and washer system operation is completely controlled by the BCM logic circuits, and that logic will only allow these systems to operate when the ignition switch is in the ACCESSORY or ON positions.

The hard wired circuits and components of the front wiper and washer system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the front wiper and washer system or the electronic controls or communication between other modules and devices that provide some features of the front wiper and washer system. The most reliable, efficient, and accurate means to diagnose the front wiper and washer system or the electronic controls and communication related to front wiper and washer system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

OPERATING MODES

Following are paragraphs that briefly describe the operation of each of the front wiper and washer system operating modes.

CONTINUOUS WIPE MODE

When the LOW position of the right (wiper) multi-function switch control stalk is selected, the switch provides a resistor multiplexed input to the BCM. The BCM responds by energizing a relay that directs battery current to the low speed brush of the wiper motor, causing the wipers to cycle at low speed.

When the HIGH position of the right (wiper) multi-function switch control stalk is selected, the switch provides a resistor multiplexed input to the BCM. The BCM responds by energizing a relay that directs battery current to the high speed brush of the wiper motor, causing the wipers to cycle at high speed.

When the OFF position of the right multi-function switch control stalk is selected, the switch provides a resistor multiplexed input to the BCM. The event that occurs depends upon the position of the wiper blades on the windshield at the moment that the control stalk 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, which provides a hard wired park switch sense input to the BCM. The BCM then de-energizes the wiper motor 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 BCM continues running the wiper motor at low speed until the wiper blades are in the down position on the windshield and the park switch input to the BCM is again closed to ground.

INTERMITTENT WIPE MODE

When the right (wiper) multi-function switch control stalk is moved to the DELAY (or INTERMITTENT) position, the switch provides a resistor multiplexed input to the BCM. The BCM electronic intermittent wipe logic circuit responds by calculating the correct length of time between wiper sweeps based upon both time and electronic vehicle speed message inputs. The BCM then provides control outputs to energize and de-energize the relays to operate the wiper motor intermittently for one low speed cycle at a time.

MIST WIPE MODE

When the right (wiper) multi-function switch control stalk is moved downward to the momentary MIST (or PULSE) position, the switch provides a resistor multiplexed input to the BCM. The BCM responds by energizing a relay that directs battery current to the low speed brush of the wiper motor, causing the wipers operate for one complete low speed cycle. The BCM can operate the front wiper motor in this mode for only one low speed cycle at a time, or for an indefinite number of sequential low speed cycles, depending upon how long the switch is held closed.

WASH MODE

When the control stalk of the right (wiper) multi-function switch is pulled rearward to the momentary front WASH position, the switch provides a resistor multiplexed input to the BCM. The BCM responds by providing battery current and ground to the washer pump/motor. This will cause the washer pump/motor to be energized in the front wash direction for as long as the switch is held closed and to be de-energized when the control stalk is released.

When the control stalk is pulled rearward to the momentary front WASH position while the front wiper system is operating in the DELAY mode, the washer pump/motor operation is the same. However, the BCM also overrides the DELAY mode and operates the front wiper motor in a continuous low speed mode for as long as the control stalk is held in the WASH position, then reverts to the DELAY mode several wipe cycles after the control stalk is released.

WIPE-AFTER-WASH MODE

When the control stalk of the right (wiper) multi-function switch is pulled rearward to the momentary front WASH position for more than about one-half second while the wiper system is not operating, the BCM directs battery current and ground to the washer pump/motor and energizes the wiper motor in a continuous low speed mode for as long as the switch is held closed. When the control stalk is released, the BCM de-energizes the washer pump/motor immediately, but allows the wiper motor to operate for several additional wipe cycles before it de-energizes the wiper motor and parks the wiper blades near the base of the windshield.

The BCM monitors the changing state of the wiper motor park switch through a hard wired wiper park switch sense circuit input. This input allows the BCM to monitor the number of wipe cycles that occur after the control stalk is released, and to determine the proper interval at which to de-energize the wiper motor to complete the WIPE-AFTER-WASH mode cycle.