Principles Of Operation

Wipers and Washers

Principles of Operation

When the ignition switch is in the RUN or ACCESSORY position, voltage is supplied to the wiper relay coil at the Battery Junction Box (BJB). The wiper relay coil is grounded at all times. Voltage is supplied to the wiper relay switch from BJB (Battery Junction Box) fuse 9. When the wiper relay is activated, voltage is supplied to the wiper motor.

Wiper Activated Headlamps (if equipped with Autolamp System)

NOTE: The Smart Junction Box (SJB) may also be identified as the Generic Electronic Module (GEM).

The SJB (Smart Junction Box) sends a voltage signal to the wiper motor in order to monitor the status of the wipers. When the headlamp control switch is in the AUTOLAMP position and the wipers on, the SJB (Smart Junction Box) will activate the headlamps within 10 seconds. When the SJB (Smart Junction Box) detects that the wipers have been turned off, the SJB (Smart Junction Box) will turn off the headlamps after 30 seconds.

High-Speed Windshield Wipers

When the multifunction switch is set to the HIGH-speed position, it supplies ground to the internal high/low-speed relay coil and the internal run/park relay coil, which causes the windshield wiper motor to operate at high speed. During HIGH-speed operation only, both the internal high/low-speed relay coil ground and the internal run/park relay coil ground are controlled directly by the multifunction switch. This differs from LOW-speed or INTERMITTENT operation when the internal run/park relay coil is controlled by the microprocessor. When the switch is placed in the OFF position, the motor continues to operate until the motor returns to the PARK position and the internal Hall-effect sensor senses the motor magnet. The output to the internal run/park relay then deactivates the relay and disconnects the voltage to the motor.

Since the internal high/low relay coil and the internal run/park relay coil are both controlled by a hard-wired circuit to the multifunction switch, the windshield wipers will still operate in HIGH-speed mode if the internal windshield wiper module fails, but will not automatically park when the multifunction switch is turned to the OFF position.

Low-Speed Windshield Wipers

When the multifunction switch is set to the LOW-speed position, it supplies ground to the internal windshield wiper motor module low-speed input and the windshield wiper motor operates at low speed. During LOW-speed operation, the internal run/park relay is activated by the microprocessor and supplies 12 volts to the low-speed brush of the windshield wiper motor. The internal run/park relay coil ground is controlled by the internal windshield wiper motor module based on inputs received from the multifunction switch. When the switch is placed in the OFF position, the motor continues to operate until the motor returns to the PARK position and the internal Hall-effect sensor senses the motor magnet. The output to the internal run/park relay then deactivates the relay and disconnects the voltage to the motor.

Intermittent-Speed Windshield Wipers

When the multifunction switch is set to the INTERMITTENT position(s), it supplies ground to the windshield wiper motor module inputs and the windshield wiper motor operates in intermittent mode. During intermittent operation, the windshield wiper motor activates the internal run/park relay coil which sends voltage through the internal high/low relay. The internal high/low relay remains deactivated, supplying the voltage to the low-speed brush of the windshield wiper motor. The windshield motor continues to operate until the internal Hall-effect sensor senses the magnet (PARK position) and deactivates the internal run/park relay, which disconnects voltage from the wiper motor. The windshield wipers remain parked until the windshield wiper motor module completes a time-out and then repeats the intermittent windshield wiper cycle.

Washer System

The windshield washer system consists of the washer reservoir and washer pump. When WASH is selected on the multifunction switch, the windshield wiper motor module activates its integral washer relay which sends voltage to the washer pump to direct fluid to the windshield.

Software Safe Mode

The windshield wiper motor defaults to software safe mode when the run/park sensor does not sense the Hall-effect magnet inside the wiper motor. This can be caused by an obstruction of the windshield wipers, a binding linkage or loss of the Hall sensor signal. The motor continues to operate in a high/low-speed condition, and when turned off, the wipers immediately park on the windshield. If necessary, the wipers can be turned on and off until they return to the PARK position.

Windshield Wiper Circuit Function Table