Principles of Operation

Wipers and Washers

Principles of Operation

Wipers and Washers

The windshield wiper system consists of a wiper relay, which is located in the Battery Junction Box (BJB) and an integrated wiper motor and module assembly, which contains internal washer, run/park and high/low speed relays. The windshield wiper motor and module assembly also contains a Hall-effect sensor that is used to determine the parked position of the wiper motor during a cycle. The integrated windshield wiper motor and module assembly has 5 different operating modes: OFF, LOW speed, HIGH speed, INTERMITTENT and SOFTWARE SAFE mode.

High-Speed Wipers

When the multifunction switch is set to the HIGH speed position, it supplies ground to the high/low speed relay coil and the run/park relay coil, which causes the windshield wiper motor to operate at high speed. During high-speed operation only, both the high/low-speed relay coil ground and the run/park relay coil ground are controlled directly by the multifunction switch. This differs from LOW speed or intermittent operation when the 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 run/park relay deactivates the relay and disconnects the voltage to the motor.

Since the high/low relay coil and the run/park relay coil are both is 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 Wipers

When the multifunction switch is set to the LOW-speed position, it supplies ground to the internal wiper motor module low-speed inputs and the 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 wiper motor. The run/park relay coil ground is controlled by the internal 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 run/park relay deactivates the relay and disconnects the voltage to the motor.

Intermittent Wipers

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

Washer

When the wash function is selected on the multifunction switch, the wiper motor module activates the integral washer relay which sends voltage to the washer pump to direct fluid to the windshield. The washer pump contains an integral check valve to control washer fluid flow-back to the washer reservoir.

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-effect 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.



Wiper Circuit Function Table