Section 51 (Wiper System & Washer System): Wipers/Washers: Operation

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 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.

In order to provide the intermittent wipe feature, the Central Timer Module (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 one-half second to about eighteen 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 sixteen kilometers-per-hour (ten miles-per-hour) the delay is driver adjustable from about one-half second to about eighteen seconds. Below about sixteen kilometers-per-hour (ten miles-per-hour) the delay times are doubled by the CTM, from about one second to about thirty-six 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, then 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 Off, 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.

The hard wired inputs to and outputs from the wiper and washer system components may be diagnosed and tested using conventional diagnostic tools and methods. Proper testing of the CTM, the PCM, or the PCI data bus vehicle speed messages requires a DRBIII(R) 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.