Windshield Wiper System Operation

The windshield wiper motor module is part of the windshield wiper motor cover and controls wiper motor operation. The accessory voltage supply circuit to the windshield wiper motor assembly is used to operate the wiper motor in all modes. The windshield wiper motor is a 2 speed motor and is operated at low speed in all modes except HIGH.

The accessory voltage supply circuit to the windshield wiper/washer switch is used to supply the windshield wiper switch signal circuits. The windshield wiper switch signal circuit voltage levels to the wiper motor module determine the wiper motor operating mode.

When the wiper/washer switch is in the LOW position voltage is supplied through a 24K ohm resistor within the switch to the windshield wiper switch signal 2 circuit, and accessory voltage is supplied to the windshield wiper switch signal 1 circuit. The reduced voltage from the wiper switch signal 2 circuit and accessory voltage from the wiper switch signal 1 circuit causes the wiper motor module to close the wiper motor accessory voltage supply circuit to the wiper motor low speed terminal.

Windshield wiper/washer system MIST operation is identical to LOW operation except that the MIST switch is a press and release type. When the wiper switch is moved to the MIST position and released, low speed wiper motor operation is started and will continue until 1 cycle is complete. If the wiper switch is moved to the MIST position and held, the windshield wiper motor will operate in the LOW mode until the switch is released.

Windshield wiper DELAY operation is a low speed wiper motor function with a variable delay interval between the wiper motor cycles. The DELAY interval is controlled through a series of resistors within the wiper/washer switch. During DELAY wiper operation the wiper switch signal 2 circuit is at the same voltage level used for LOW operation, but the wiper switch signal 1 circuit voltage is reduced through the DELAY resistors. The windshield wiper motor module uses a capacitor feed by the wiper switch signal 1 circuit to determine the frequency of the low speed wiper motor cycles. When the wiper switch signal 1 circuit is at the accessory voltage level as in the LOW switch position, the capacitor charges fast causing continuous low speed wiper motor operation. The DELAY switch position indicating the longest interval between wiper motor cycles is the switch position with the highest resistance resulting in low voltage on the wiper switch signal 1 circuit. The low voltage charges the capacitor slowly causing a long delay interval between wiper motor cycles. As the DELAY switch is turned to positions indicating more frequent wiper cycles, the resistance through the wiper/washer switch is reduced and the wiper switch signal 1 circuit voltage increases. When the wiper switch signal 1 circuit voltage increases the capacitor charges faster and the delay interval between wiper motor cycles decreases.

When the wiper/washer switch is in the HIGH position the accessory voltage to the wiper/washer switch is closed to the high speed signal circuit. The accessory voltage on the high speed signal circuit causes the wiper motor module to close the wiper motor accessory voltage supply circuit to the wiper motor high speed terminal. During HIGH speed wiper motor operation the wiper switch signal 1 and signal 2 circuits are at the LOW speed signal voltages, but the LOW speed signal circuit inputs to the wiper motor module are overridden by the active HIGH speed signal circuit.

The windshield wiper/washer system WASH function uses 2 switch contacts within the wiper/washer switch assembly. One switch contact closes the wiper/washer switch accessory voltage supply circuit to the wiper switch signal 2 circuit. Accessory voltage on the wiper switch signal 2 circuit causes the wiper motor module to close the wiper motor accessory voltage supply circuit to the wiper motor low speed terminal. The WASH command on the wiper switch signal 2 circuit will cause the wiper motor to operate at low speed for as long as the switch is held in the closed position and approximately 6 seconds after being released. The other WASH switch contact in the wiper/washer switch is the control circuit to the windshield washer pump. When the WASH switch is in the held in the closed position the wiper/washer switch accessory voltage supply circuit is used to operate the windshield washer pump until the switch is released.

Windshield wiper motor park operation is controlled by the wiper motor module using an input from the park switch within the wiper motor assembly. When the windshield wiper/washer switch is turned to the OFF position while the wiper motor is somewhere in mid-cycle, the wiper motor module will continue to operate the wiper motor until the wipers reach the park position.

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Comments (5)
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  • Guest - Roger Hosmer

    1999 chevy silverado wiper control board capacitor blown on board delays dont work but high speed does due to heavy snow.going to install new board .is there anything more I should look at .

  • Guest - Dennis

    The park function in my 2000 Windstar windshield wiper system operates erratically. The wipers park at random positions and after a while, do not operate at all when the intermittent mode is selected. What do I replace to restore correct park operation? Thank you.

  • Guest - clark

    Great

  • Guest - Guest

    :-x

  • Guest - dixie normous

    In reply to: Guest - Guest

    good one g