Wiper and Washer Systems: Description and Operation

CIRCUIT OPERATION
When the Ignition Switch is in the "ACCY" or "RUN" position, power is available to the Controller Assembly.

When the Wash Switch is momentarily closed, the Washer Pump Motor is grounded, and current flows through the Controller Assembly to operate the washer. The washer can be operated with the Wiper Switch in any position. If the Wiper Switch is in the "OFF" position, the Controller Assembly turns on power to the Wiper Motor for 3 to 5 low-speed sweeps and then turns power OFF.

The Wiper Motor also operates when the Wiper Switch is set to "LOW", "HIGH", "DELAY", or "MIST".

With the Wiper Switch in any of these positions, the Park Relay is energized (92 circuit). The Park Relay contacts by-pass the Park Switch when the wipers are operating, and current flows through the Controller Assembly, through the Wiper Motor, and through the Wiper Switch to ground. When the Wiper Switch is moved to "OFF", the Park Relay contacts open, and the Park Switch supplies motor power. The wipers operate at "LOW" speed until the wipers are parked.

Wiper Motor speed is controlled by the section of the Wiper Switch connected to the Wiper Motor (91 circuit). The Wiper Motor operates at "LOW" speed when its Shunt Field coil is grounded through the 91 circuit. The Wiper Motor operates at "HIGH" speed when its Shunt Field is grounded through the 20 ohm resistor located inside the Wiper Motor.

With the Wiper Switch set to "DELAY", the amount of delay between wipes is controlled by rotating the Delay Rheostat knob. The Controller Assembly determines the time between sweeps. The longest time is obtained by rotating the knob fully counterclockwise. With the knob rotated fully clockwise, the wipers operate at LOW speed without any delay.

By momentarily pressing the Wiper Switch to "MIST", the Wiper Motor operates at "LOW" speed. When the Wiper Switch is released, the wiper returns to "PARK" position.

The Wiper Motor contains a Circuit Breaker which removes power temporarily if the motor is stalled.