Principles of Operation

PRINCIPLES OF OPERATION

The windshield wiper motor receives inputs from the following:
- Multi-function switch
- Lighting control module (LCM)
- Ignition switch
- Battery junction box (BJB)
- Central junction box (CJB)

The following components are integrated into the windshield wiper motor:
- Windshield wiper motor module
- High/low speed relay
- Run/park sensor (Hall effect)
- Washer pump relay

If equipped with automatic headlamps, the LCM will illuminate the exterior lamps, including the parking lamps, when the front wipers are on for more than 10 seconds.

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

Since the integral high/low relay coil and the integral run/park relay coil are both controlled by a hard wired circuit to the multi-function 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 multi-function switch is turned to the OFF position.

Low-Speed
When the multi-function switch is set to the low-speed position, it supplies ground to the internal windshield wiper motor module low-speed inputs and the windshield wiper motor operates at low speed. During low-speed operation, the integral run/park relay is activated by the microprocessor and supplies 12 volts to the low-speed brush of the windshield wiper motor. The integral run/park relay coil ground is controlled by the internal windshield wiper motor module based on inputs received from the multi-function 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 integral run/park relay deactivates the relay and disconnects the voltage to the motor.

Since the integral 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 multi-function switch is turned to the OFF position. This is due to the integral run/park and integral 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
When the multi-function 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 integral run/park relay coil which sends voltage through the integral high/low relay. The integral 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 integral 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 multi-function 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: