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WIPERS/WASHERSAn electrically operated intermittent wiper and washer system is standard factory-installed safety equipment on this model.
The AN or AN84 truck utilize speed sensitive intermittent wipers. The low and high speeds are controlled through the wiper stalk switch. The intermittent portion of the wiper control is handled by the CTM through the intermittent wiper relay. When the module detects a decrease in delay time as selected by the driver, an immediate wipe of the windshield takes place and the new delay interval is implemented.
The wiper and washer system includes the following major components, which are described in further detail elsewhere in this service information:
- Central Timer Module - The Central Timer Module (CTM) is located on the left cowl side inner panel under the driver side outboard end of the instrument panel. The CTM contains a microprocessor and software that allow it to provide the many electronic functions and features not available with most conventional hard wired wiper and washer systems. The CTM provides the proper wiper and washer system features based upon the monitored inputs. The CTM circuitry monitors hard wired switch inputs, as well as message inputs received from other vehicle electronic modules on the Programmable Communications Interface (PCI) data bus network. (Refer to ELECTRONIC CONTROL MODULES/BODY CONTROL/CENTRAL TIMER MODULE - DESCRIPTION).
- Multi-Function Switch - The multi-function switch is secured to the left side of the steering column, just below the steering wheel. Only the control stalk for the multi-function switch is visible, the remainder of the switch is concealed beneath the steering column shrouds. The multi-function switch contains all of the switches for both the wiper and washer systems.(Refer to LAMPS/LIGHTING - EXTERIOR/MULTI-FUNCTION SWITCH - DESCRIPTION)
- Washer Fluid Level Switch - The washer fluid level switch is located in a dedicated hole near the front of the windshield washer reservoir on the right outboard end of the upper radiator shroud.
- Washer Nozzles - The dual 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. The washer plumbing fittings for the washer nozzles are concealed beneath the cowl plenum cover/grille panel.
- Washer Pump/Motor - The washer pump/motor unit is located in a dedicated hole near the bottom of the windshield washer reservoir on the right end of the upper radiator shroud.
- Washer Reservoir - The washer reservoir is integral to and located on the right end of the upper radiator shroud. The washer reservoir filler is accessed from the right front corner of the engine compartment.
- Wiper Arms - The two wiper arms are secured to the two wiper pivots, which extend through the cowl plenum cover/grille panel located near the base of the windshield.
- Wiper Blades - The two wiper blades are secured to the two wiper arms, and are parked on the glass near the bottom of the windshield when the wiper system is not in operation.
- Wiper Module - The wiper pivots are the only visible components of the wiper module. The remainder of the module is concealed within the cowl plenum beneath the cowl plenum cover/grille panel. The wiper module includes the module bracket, the single wiper motor, the wiper linkage, and the two wiper pivots.
- Wiper Relay - The wiper relay is located in the Power Distribution Center (PDC) in the engine compartment near the battery.
Features of the wiper and washer system include the following:
- Continuous Wipe Modes - The two-speed wiper motor and the internal circuitry of the multi- function switch work in concert to provide two continuous wipe cycles, low speed or high speed.
- Intermittent Wipe Mode - The internal circuitry of the multi-function switch, the CTM, and the wiper relay work in concert to provide an intermittent wipe mode with multiple delay interval selections. The CTM also automatically adjusts each manually selected delay interval to compensate for vehicle speed.
- Washer Mode - When the washer system is activated with the multi-function switch while the wiper system is operating, washer fluid will be dispensed onto the windshield glass through the washer nozzles for as long as the washer pump/motor is energized.
- Wipe-After-Wash Mode - The internal circuitry of the CTM provides a wipe-after-wash feature which, if the wipers are turned OFF, will operate the washer pump/motor and the wipers for as long as the washer system is activated, then provide several additional wipe cycles after the washer system is deactivated before parking the wiper blades near the base of the windshield.
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 intended 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 that might be encountered while driving the vehicle under numerous types of inclement operating conditions from the outside windshield glass surface. The vehicle operator initiates all wiper and washer system functions with the multi-function switch control stalk that extends from the left side of the steering column, just below the steering wheel. Rotating the knob on the end of the multi-function switch control stalk selects the desired wiper system operating mode. The wiper system allows the vehicle operator to select from two continuous wiper speeds, Hi or Lo, or one of several intermittent wipe Delay mode intervals. Pushing the knob on the end of the control stalk towards the steering column activates the washer pump/motor, which dispenses washer fluid onto the windshield glass through the washer nozzles.
When the ignition switch is in the ACCESSORY or ON positions, battery current from a fuse in the Junction Block (JB) is provided through a fused ignition switch output (RUN/ACC) circuit to the wiper motor park switch, the wiper relay and the multi-function switch. The internal circuitry of the multi-function switch provides a direct hard wired battery current output to the low speed or high speed brushes of the wiper motor when the Lo or Hi switch setting is selected, which causes the wipers to cycle at the selected speed. The intermittent wipe, and wipe-after-wash features of the wiper and washer system are provided by the electronic intermittent wipe logic circuit within the Central Timer Module (CTM). In order to provide the intermittent wipe feature, the CTM monitors the wiper switch state and the wiper motor park switch state. In order to provide the wipe-after-wash feature, the CTM monitors both the washer switch state and the wiper motor park switch state. When a Delay position is selected with the multi-function switch control knob, the CTM logic circuit responds by calculating the correct delay interval. The CTM then energizes the wiper relay by pulling the relay control coil to ground. The energized wiper relay directs battery current through the normally open contact of the relay back through the internal Delay position circuitry of the multi-function switch to the low speed brush of the wiper motor. The CTM monitors the wiper motor operation through the wiper park switch sense circuit, which allows the CTM to determine the proper timing to begin the next wiper blade sweep. The normal delay intervals are driver adjustable from about 1/2 second to about 18 seconds.
The CTM also provides a speed sensitive intermittent wipe feature. By monitoring vehicle speed messages received from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus network, the CTM is able to adjust the delay intervals to compensate for vehicle speed. Above about 16 km/h (10 mph) the delay is driver adjustable from about 1/2 second to about 18 seconds. Below about 16 km/h (10 mph) the delay times are doubled by the CTM, from about one second to about 36 seconds.
When the OFF position of the multi-function switch wiper control knob is selected, one of two events is possible. The event that will occur depends upon the position of the wiper blades on the windshield at the moment that the 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 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 closed to battery current through a fused ignition switch output (RUN/ACC) circuit. The park switch sense circuit directs this battery current to the low speed brush of the wiper motor through the normally closed contact of the wiper relay and the internal OFF position circuitry of the multi-function switch. This causes the wiper motor to continue running until the wiper blades are in the down position on the windshield and the park switch is again closed to ground.
When the Wash position of the multi-function switch is selected, the Wash position circuitry within the switch directs a battery current signal input to the CTM. The CTM monitors the washer switch state through this input to control a battery current output to the washer pump/motor unit. When the washer switch is closed with the wiper system turned Of{ the CTM operates the wiper motor through the wiper relay in the same manner as it does to provide the Delay mode operation. After the state of the washer switch changes to open, the CTM monitors the wiper motor through the wiper park switch sense circuit, which allows the CTM to monitor the number of wiper blade sweeps. After the appropriate number of wiper sweeps, the CTM de-energizes the wiper relay and the wipers return to their park position.
Proper testing of the CTM, the PCM, or the PCI data bus vehicle speed messages requires a DRB III scan tool. Refer to the appropriate diagnostic information. Refer to the owner's manual in the vehicle glove box for more information on the features and operation of the wiper and washer system.
CHECK VALVE
A washer system check valve is standard equipment on this model The check valve is integral to the washer nozzle plumbing wye fitting located in the cowl plenum beneath the cowl plenum coven grille panel near the base of the windshield. The check valve consists of a molded plastic body with a round center section. Three barbed hose nipples are formed in a wye configuration on the outside circumference of the center section of the valve body Within the check valve body, a small check valve operated by a small coiled spring restricts flow through the unit until the valve is unseated by a predetermined inlet fluid pressure. The check valve cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
The check valve provides more than one function in this application. It serves as a wye connector fitting between the cowl grille panel and washer nozzle sections of the washer supply hose. It also prevents washer fluid from draining out of the washer supply hoses back to the washer reservoir. This drain-back would result in a lengthy delay from when the washer switch is actuated until washer fluid was dispensed through the washer nozzles, because the washer pump would have to refill the washer plumbing from the reservoir to the nozzles. Finally the check valve prevents washer fluid from siphoning through the washer nozzles after the washer system is turned OFF.
Within the check valve body, a small check valve is held in place against a seat by a small coiled spring to restrict flow through the unit until the valve is unseated by a predetermined inlet fluid pressure. When the washer pump pressurizes and pumps washer fluid from the reservoir through the washer plumbing, the fluid pressure overrides the spring pressure applied to the check valve and unseats the valve, allowing washer fluid to flow toward the washer nozzles. When the washer pump stops operating, spring pressure seats the check valve and fluid flow in either direction within the washer plumbing is prevented.
WASHER FLUID LEVEL SWITCH
The washer fluid level switch is a single pole, single throw reed-type switch mounted on the outboard side of the washer reservoir forward of the washer pump/motor, in the right front corner of the engine compartment. Only the molded plastic switch mounting flange and connector receptacle are visible when the switch is installed in the reservoir. A short nipple formation extends from the inner surface of the switch mounting flange, and a barb on the nipple near the switch mounting flange is press-fit into a rubber grommet seal installed in the mounting hole of the reservoir. A small plastic float pivots on the end of a bracket that extends from the switch nipple formation. Within the float is a small magnet, which actuates the reed switch. The washer fluid level switch cannot be adjusted or repaired. If faulty or damaged, the switch must be replaced.
The washer fluid level switch uses a pivoting, oblong float to monitor the level of the washer fluid in the washer reservoir. The float contains a small magnet. When the float pivots, the changing proximity of its magnetic field will cause the contacts of the small, stationary reed switch to open or close. When the fluid level in the washer reservoir is at or above the float level, the float moves to a vertical position and the switch contacts open. When the fluid level in the washer reservoir falls below the pivoting float, the float moves to a horizontal position and the switch contacts close. The switch contacts are connected in series between ground and the washer fluid switch sense input of the instrument cluster. The switch is connected to the vehicle electrical system through a dedicated take out and connector of the headlamp and dash wire harness. The switch receives ground through another take out of the headlamp and dash wire harness with a single wyelet terminal connector that is secured under a nut to a ground stud located on the right front fender inner shield in the engine compartment. The washer fluid level switch can be diagnosed using conventional diagnostic tools and methods. (Refer to WASHER FLUID INDICATOR - DIAGNOSIS AND TESTING).