Wiper and Washer Systems: Description and Operation

Front Wiper/Washer

How the Circuit Works
The wiper/washer system is a multiplex controlled system. The MICU and wiper/washer switch are the main operation controls of the front wiper/washer system.

Testing of the MICU and the reading of Diagnostic Trouble Codes (DTC's) within the multiplex integrated control system can be done by using a HDS Tester. (There are more than 80 multiplex system DTC's.) The windshield wiper motor and washer motor can still be tested manually without a HDS Tester.

Power Supply
With the ignition switch in ON (II) or START (III), battery voltage is supplied through fuses 10 and 38 (in the under-dash fuse/relay box) to the MICU.

Mist
When the windshield wiper switch is moved to MIST the signal for mist is input to the MICU. The MICU supplies battery voltage to the high winding of the windshield wiper motor, causing the motor to run in high. As soon as the motor starts running, the mechanical park/run switch built in the motor will move from PARK to RUN. With the motor running, the mechanical park/run switch is in RUN removing ground from the FR WIP AS input to the MICU. If the switch is held in MIST for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN indicating what position the wipers are in to the MICU.

Intermittent
When the windshield wiper switch is moved to INTERMITTENT the signal for intermittent and the signal for the intermittent dwell time controller are inputted to the MICU. The MICU supplies battery voltage to the low winding of the windshield wiper motor causing the motor to run in low. As soon as the motor starts running, the mechanical park/run switch built in the motor will move from PARK to RUN. With the motor running, the mechanical park/run switch is in RUN, removing ground from the FR WIP AS input to the MICU. If the switch is in INTERMITTENT for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN, indicating what position the wipers are in to the MICU.

Low Speed
When the windshield wiper switch is moved to LOW, the signal for low is input to the MICU. The MICU supplies battery voltage to the low winding of the windshield wiper motor, causing the motor to run in low. As soon as the motor starts running, the mechanical park/run switch built in the motor will move from PARK to RUN. With the motor running, the mechanical park/run switch is in RUN, removing ground from the FR WIP AS input to the MICU. If the switch is in LOW for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN, indicating what position the wipers are in to the MICU.

When the windshield wiper switch is moved to OFF the signal for off is input to the MICU. Once the wipers reach the PARK position, the MICU removes battery voltage from the low winding of the windshield wiper motor.

High Speed
When the windshield wiper switch is moved to HIGH, the signal for high is input to the MICU. The MICU supplies battery voltage to the high winding of the windshield wiper motor, causing the motor to run in high. As soon as the motor starts running, the mechanical park/run switch built in the motor will move from PARK to RUN. With the motor running, the mechanical park/run switch is in RUN, removing ground from the FR WIP AS input to the MICU. If the switch is in HIGH for multiple wiper cycles, the PARK/RUN signal will alternate between PARK and RUN, indicating what position the wipers are in to the MICU.

When the windshield wiper switch is moved to OFF the signal for off is input to the MICU. Once the wipers reach the PARK position, the MICU removes battery voltage from the high winding of the windshield wiper motor.

Washer
When the windshield wiper switch is moved to WASH, the signal for wash is inputted to the MICU. The MICU supplies battery voltage to the windshield washer motor and to the high winding of the windshield wiper motor. The windshield washer motor pumps washer fluid onto the windshield, and the windshield wiper motor runs in high. As soon as the wiper motor starts running, the mechanical park/run switch built in the motor will move from PARK to RUN.