Wiper and Washer Systems: Description and Operation

Wiper/Washer

How the Circuit Works
The wiper/washer system is a multiplex controlled system. A combination switch control unit, MICU, and relay control module are the main operation controls of the wiper/washer system. The washer motor relay, intermittent wiper relay, and windshield wiper high relay are incorporated in the relay control module.

Testing the control unit components and reading Diagnostic Trouble Codes (DTC's) within the multiplex control system can be done by using Honda PGM Tester/HDS equipment. There are more than 80 multiplex system DTC's. The wiper motor and washer motor can still be tested manually without the PGM Tester/HDS equipment.

Power Supply
With the ignition switch in the ON (II) or START (III) position, battery voltage is applied to the windshield wiper motor through fuse 11 (in the under-dash fuse/relay box).

Also, with the ignition switch in the ON (II) or START (III) position, battery voltage is applied through fuse 21 (in the under-dash fuse/relay box) to the following control units:
- Combination switch control unit
- MICU
- Relay control module

Fuse 7 (in the under-dash fuse/relay box) is hot at all times and supplies battery voltage to the combination switch control unit and the MICU.

With the ignition switch in the ON (II) or START (III) position, fuse 20 (in the under-dash fuse/relay box) supplies battery voltage to the windshield washer motor.

Low Speed
When you move the wiper switch to the LOW position, the combination switch control unit is internally grounded notifying the combination switch control unit of the request. The low-speed wiper request is communicated from module-to-module across the multiplex communication lines. The relay control module will operate the intermittent and windshield wiper high relay as needed to ground the low speed winding of the wiper motor for low speed operation.

High Speed
When you move the wiper switch to the HIGH position, the combination switch control unit is internally grounded, notifying the combination switch control unit of the request. The high-speed wiper request is communicated from module-to-module across the multiplex communication lines. The relay control module will then operate the intermittent and high wiper relay as needed to ground the high-speed winding of the wiper motor for high-speed operation.

Intermittent
When you move the wiper switch to the INTERMITTENT position, the combination switch control unit is internally grounded, notifying the combination switch control unit of the request. The wiper sweep interval is controlled by the vehicle speed and the resistance of the intermittent wiper dwell time controller. The intermittent wiper request is communicated from module-to-module across the multiplex communication lines. The relay control module will operate the intermittent and high wiper relay as needed to ground the low speed winding of the wiper motor for low speed intermittent operation.

Mist
When you push the wiper/washer lever up to the mist position, the combination switch control unit is internally grounded, notifying the combination switch control unit of the request. The mist request is communicated from module-to-module across the multiplex communication lines. The relay control module will operate the intermittent and high wiper relay as needed to ground the low-speed winding of the wiper motor for low-speed mist operation. The wipers sweep at low-speed until you release the lever. The PARK/OFF function then takes over when the lever is released, and the wipers stop in the PARK position.

Washer
When you pull the wiper/washer lever, the combination switch control unit is internally grounded, notifying the combination switch control unit of the request. The washer request is communicated from module-to-module across the multiplex communication lines. The relay control module will operate the washer motor relay to ground the winding of the washer motor, allowing it to pump fluid onto the windshield. The wipers sweep at low-speed and will complete one more sweep after you release the washer lever. The PARK/OFF function then takes over, and the wipers stop in the PARK position.

Park/Off
When you move the wiper switch to the PARK/OFF position, the combination switch control unit is internally grounded, notifying the combination switch control unit of the request. The park/off wiper request is communicated from module-to-module across the multiplex communication lines. The relay control module will operate the intermittent and the high wiper relay as needed for park/off wiper operation.