Wiper and Washer Systems: Description and Operation

WIPERS AND WASHERS

The windshield wiper/washer system consists of the following components:
- Multifunction switch
- Windshield wiper blades
- Windshield wiper pivot arms
- Windshield wiper mounting arm and pivot shaft assembly
- Windshield wiper motor
- Smart junction box (SJB)
- Windshield wiper switch
- Windshield washer nozzle
- Windshield washer reservoir
- Windshield washer pump

The wiper system is activated by the multifunction switch. The multifunction switch provides input to the front wiper motor module to activate wash, low, high and intermittent modes. The relays are all integral to the wiper motor module and are riot serviceable separately. The washer system consists of the washer reservoir and washer pump. When the multifunction switch is placed into the wash mode, the windshield wiper motor integral electronics activate the washer pump to direct washer fluid to the windshield.

Principles of Operation
The following components are integrated in the wiper motors:
- Windshield wiper motor module
- Run/park relay
- High/low speed relay
- Run/park sense (Hall effect)
- Washer pump relay

High Speed Windshield 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 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 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 run/park relay deactivates the relay and disconnects the voltage to the motor.
Since the run/park relay is controlled by the internal windshield wiper motor microprocessor, the wipers will only operate in high speed mode if the internal windshield wiper motor module fails, and will not automatically park when the multifunction switch is turned to the OFF position. This is due to the run/park and high/low relay coils being directly hard-wired to the switch in high speed. The diode prevents current flow through the high/low relay coil so the relay remains in the normally closed LOW speed position.

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 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 windshield wiper motor. The windshield 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 windshield wiper motor module completes a time-out and then repeats the intermittent windshield wiper cycle.

Washer System
When windshield 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 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.