OPERATION
The wiper and washer system is designed to provide
the vehicle operator with a convenient, safe, and reli-
able means of maintaining visibility through the wind-
shield 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 (1) on the end of the
control stalk (2) 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 momen-
tary 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 multi-function switch provides hard wired resistor multiplexed
inputs to the ElectroMechanical Instrument Cluster (EMIC) for all of the wiper and washer system functions. The
EMIC 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)/Power Distribution Center (PDC)
to the wiper on/off relay and the wiper high/low relay in the IPM/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 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 con-
ventional diagnostic tools and methods. However, conventional diagnostic methods may not prove conclusive in the
diagnosis of the EMIC, the FCM, or the electronic message inputs to or outputs from the EMIC or the FCM that
control the wiper and washer system operating modes. The most reliable, efficient, and accurate means to diagnose
the EMIC or the FCM inputs and outputs related to the various wiper and washer system operating modes 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 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 EMIC
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
8R - 48
WIPERS/WASHERS - SERVICE INFORMATION
DR/DH