Wiper and Washer Systems: Description and Operation

Fig.1 Wiper And Washer System:

WIPERS/WASHERS
An electrically operated intermittent wiper and washer system is standard factory-installed safety equipment on this model. The wiper and washer system includes the following major components, which are described in further detail elsewhere in this service information:

- Check Valve - The washer system check valve is integral to the wye fitting located in the washer plumbing between the cowl plenum washer hose and the washer nozzles, and is concealed beneath the cowl plenum cover/grille panel at the base of the windshield.

- Front Control Module - The Front Control Module (FCM) is integral to the Integrated Power Module (IPM). The IPM is located in the engine compartment, near the battery.

- Instrument Cluster - In this model, the instrument cluster is also sometimes referred to as the Cab Control Node (CCN). The instrument cluster is located in the instrument panel above the steering column opening, directly in front of the driver.

- Multi-Function Switch - The multi-function switch is located on the top of the steering column, just below the steering wheel. The multi-function switch includes a control stalk that extends through an opening on the left side of the steering column shrouds and a control knob on the end of the stalk is dedicated to providing all of the driver controls for the wiper and washer systems.

- Washer Fluid Level Switch - The washer fluid level switch is located in a dedicated hole on the outboard side of the washer reservoir in the engine compartment.

- Washer Nozzle - Two fluidic washer nozzles are secured with integral snap features to dedicated openings in the cowl plenum cover/grille panel located near the base of the windshield.

- Washer Plumbing - The plumbing for the washer system consists of rubber hoses and molded plastic fittings. The plumbing is routed along the right side of the engine compartment from the washer reservoir, and through a trough near the right end of the cowl plenum cover/grille panel into the cowl plenum to the washer nozzle fittings.

- Washer Pump/Motor - The electric washer pump/motor unit is located in a dedicated hole on the rearward facing surface of the washer reservoir in the engine compartment.

- Washer Reservoir - On all models except those with an optional V-10 or diesel engine, the washer reservoir is secured by integral mounting tabs and a snap feature to slots in the right side of the cooling module shroud in the engine compartment. On models with an optional V-10 or diesel engine, the washer reservoir is secured by screws to the back of the upright left vertical member of the radiator support in the engine compartment. The washer reservoir filler neck is accessed from the engine compartment.

- Wiper Arm - The two wiper arms are secured with integral latches to the serrated ends of the two wiper pivot shafts, which extend through the cowl plenum cover/grille panel located near the base of the windshield.

- Wiper Blade - The two wiper blades are secured to the two wiper arms with an integral latch, and are parked on the glass near the bottom of the windshield when the wiper system is not in operation.

- Wiper High/Low Relay - The wiper high/low relay is an International Standards Organization (ISO) micro relay located in the Integrated Power Module (IPM) in the engine compartment near the battery.

- Wiper Module - The wiper pivot shafts are the only visible components of the wiper module. The remainder of the module is concealed within the cowl plenum area beneath the cowl plenum cover/grille panel. The wiper module includes the wiper module bracket, four rubber-isolated wiper module mounts, the wiper motor, the wiper motor crank arm, the two wiper drive links, and the two wiper pivots.

- Wiper On/Off Relay - The wiper on/off relay is an International Standards Organization (ISO) micro relay located in the Integrated Power Module (IPM) in the engine compartment near the battery.

Hard wired circuitry connects the wiper and washer system components to the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the wiper and washer system components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

The 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 outside windshield glass surface that might be encountered while driving the vehicle under numerous types of inclement operating conditions.

The vehicle operator initiates all wiper and washer system functions with the control knob on the end of the control stalk of the multi-function switch that extends from the left side of the steering column, just below the steering wheel. Rotating the control knob on the end of the control stalk, selects the Off, Delay, Low, or High wiper system operating modes. In the Delay mode, the control knob also allows the vehicle operator to select from one of five intermittent wipe Delay intervals. Depressing the control knob towards the steering column actuates the momentary washer system switch, which selects the Wash, Wipe-After-Wash, and Pulse Wipe Modes depending upon when and how long the switch is held closed. The multifunction switch provides hard wired resistor multiplexed inputs to the instrument cluster for all of the wiper and washer system functions. The instrument cluster then sends electronic messages to the Front Control Module (FCM) over the Programmable Communications Interface (PCI) data bus requesting the appropriate wiper and washer system operating modes.

Wiper and washer system operation are completely controlled by the instrument cluster and FCM logic circuits, and that logic will only allow 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 IPM 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 a high side driver to control the operation of the washer pump motor unit. The multi-function switch circuitry receives a clean ground output from the instrument cluster on a multi-function switch return circuit, then provides resistor multiplexed inputs to the instrument cluster 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.

The hard wired circuits and components of the wiper and washer system may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the instrument cluster, the FCM, or the electronic message inputs to or outputs from the instrument cluster or FCM that control the wiper and washer system operating modes. The most reliable, efficient, and accurate means to diagnose the instrument cluster or the FCM inputs and outputs related to the various wiper and washer system operating modes requires the use of a DRBIII scan tool. Refer to the appropriate diagnostic information.

OPERATING MODES
The components of the wiper and washer system are designed to work in concert to provide the following operating modes:

- Continuous Wipe Mode - The control knob on the control stalk of the multi-function switch has two continuous wipe positions, Low and High. When selected, these switch positions will cause the two-speed wiper motor to operate in a continuous low or high speed cycle.

- Intermittent Wipe Mode - The control knob on the control stalk of the multi-function switch has five minor detent intermittent wipe positions. When selected, these switch positions will cause the wiper system to operate with one of five delay intervals between complete wipe cycles. The intermittent wipe delay intervals are speed sensitive and will be doubled when the vehicle speed is about 16 km/h (10 mph) or less.

- Pulse Wipe Mode - When the control knob on the control stalk of the multi-function switch is depressed to the momentary Wash position for less than about one-half second, the wiper system will operate the wipers for one complete low speed cycle, then will park the wiper blades near the base of the windshield.

- Washer Mode - When the control knob on the control stalk of the multi-function switch is depressed to the momentary Wash position for more than about one-half second with the wiper system turned Off, the washer pump/motor and the wipers will operate for as long as the washer switch is held closed up to about thirty seconds, then the wipe-after-wash mode is invoked when the control knob is released. When the Wash position is selected with the wiper system operating in a continuous wipe mode, washer fluid will be dispensed onto the windshield glass through the washer nozzles for as long as the washer switch is held closed up to about thirty seconds. When the Wash position is selected with the wiper system operating in an intermittent wipe mode, washer fluid is still dispensed until the control knob is released; however, the wipers will operate in a low speed continuous cycle from the time the washer switch is closed until several wipe cycles after the switch is released, before returning to the selected intermittent wipe interval. If the control knob is held in the depressed Wash position for more than about 30 seconds, washer system operation will be suspended until the control knob is released for about two seconds then cycled back to the Wash position.

- Wipe-After-Wash Mode - When the control knob on the control stalk of the multi-function switch is depressed to the momentary Wash position for more than about one-half second with the wiper system turned Off, the washer pump/motor and the wipers will operate for as long as the washer switch is held closed up to about thirty seconds, then provide several additional wipe cycles after the control knob is released before parking the wiper blades near the base of the windshield. If the control knob is held in the depressed Wash position for more than about thirty seconds, washer system operation will be suspended until the control knob is released for about two seconds then cycled back to the Wash position.

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

Continuous Wipe Mode
When the Low position of the control knob on the control stalk of the multi-function switch is selected the instrument cluster sends an electronic wiper switch low message to the FCM, then the FCM energizes the wiper on/off relay. This directs battery current 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 to the low speed brush of the wiper motor, causing the wipers to cycle at low speed.

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

When the Off position of the multi-function switch control knob is selected, the instrument cluster 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. Then one of two events will occur. The event that occurs depends upon 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, which causes 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.

Intermittent Wipe Mode
When the control knob on the control stalk of the multi-function switch is moved to one of the Delay interval positions the instrument cluster 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 hard wired 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 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 about 16 km/h (10 mph) or less.

Pulse Wipe Mode
When the control knob on the control stalk of the multi-function switch is depressed to the momentary Wash position for less than about one-half second, the instrument cluster sends an electronic washer switch message to the FCM, then the FCM the 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 on the control stalk of the multi-function switch is depressed to the momentary Wash position for more than about one-half second, the instrument cluster sends an electronic washer switch message to the FCM, then the FCM directs battery current to the washer pump/motor unit. This will cause the washer pump/motor unit to be energized for as long as the Wash switch is held closed up to about thirty seconds, and to de-energize when the front Wash switch is released.

When the control knob is depressed to the momentary Wash position while the wiper system is operating in one of the Delay 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 depressed, 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 depressed for more than about thirty seconds, the FCM will suspend washer pump/motor operation until the knob is released for about two seconds, then cycled back to the Wash position.

Wipe-after-Wash Mode
When the control knob on the control stalk of the multi-function switch is depressed to the momentary Wash position for more than about one-half second while the wiper system is not operating, the instrument cluster sends an electronic washer switch message to the FCM, then the FCM the directs battery current to the washer pump/motor unit and energizes the wiper on/off relay. This will cause 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 thirty 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 depressed for more than about thirty seconds, the FCM will suspend washer pump/motor operation until the knob is released for about two seconds, then cycled back to the Wash position; however, the wipers will 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 hard wired 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.