OPERATING MODES
Following are paragraphs that briefly describe the operation of each of the rear wiper and washer system operating
modes.
CONTINUOUS WIPE MODE
When the On position of the rear wiper/washer control knob is selected the instrument cluster sends an electronic
wiper switch message to the FCM, then the FCM energizes the rear wiper relay. This directs battery current to the
rear wiper motor, causing the wiper to cycle continuously at a fixed speed until the FCM de-energizes the rear wiper
relay.
INTERMITTENT WIPE MODE
When the rear wiper/washer control knob 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 rear 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
rear wiper relay to operate the wiper motor intermittently for one cycle at a time.
WASH MODE
When the rear wiper/washer control knob is depressed to the momentary Wash position, the instrument cluster
sends an electronic washer switch message to the FCM, then the FCM directs battery current and ground 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 rear wiper/washer control knob is
released.
WIPE-AFTER-WASH MODE
When the rear wiper/washer control knob is released from the momentary Wash position, the instrument cluster
sends an electronic washer switch message to the FCM. The FCM de-energizes the washer pump/motor, but allows
the rear wiper motor to operate for several wipe cycles before it de-energizes the rear wiper relay.
OFF MODE
When the Off position of the rear wiper/washer control knob is selected, one of three events is possible. The event
that will occur depends upon the position of the wiper blade on the liftgate glass and the mode the wiper motor is
operating under at the moment that the Off position is selected. If the wiper blade is in the down position on the
glass and the rear wiper system is operating in the fixed or fixed intermittent cycle modes when the Off position is
selected, the park switch is open and the FCM de-energizes the rear wiper relay control coil causing the rear wiper
motor to cease to operation.
If the wiper blade is not in the down position on the glass and is operating in the fixed or fixed intermittent cycle
modes when the Off position is selected, the park switch is closed to ground and the FCM keeps the rear wiper
relay control coil energized to operate the rear wiper motor until the rear wiper blade is in the down position on the
glass and the park switch input is an open circuit.
The third event occurs with the rear wiper operating in the wipe-after-wash mode when the Off position is selected,
in which case the FCM will continue to run the wiper motor until the completion of about three wiper blade sweeps
before the rear wiper blade is parked. The FCM will also run the rear wiper motor to park the rear wiper blade if the
ignition switch is turned to the Off position while the rear wiper system is still operating.
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REAR WIPERS/WASHERS - SERVICE INFORMATION
8R - 75