Wiper and Washer Systems: Description and Operation

The Interval Wiper/Washer allows the driver to select three wiper speeds: LO, HI or INT (Interval). In INT, wipes can be spaced one second to fifteen seconds apart.

The Interval Wiper/Washer Control has a momentary Washer Switch, a four-position Wipe Switch, and an Interval Time Adjust knob on the end of the lever.

Washer Operation

Pushing in the knob on the Wiper/Washer Switch sends current from the Wiper Circuit Breaker through the Washer Switch to the Interval Governor and the Washer Pump. If the Wiper Switch is in LO or HI, normal wipe action occurs during washing. If the Wiper Switch is in OFF or INT, Interval Override operates the Electronic Switch and the Governor Relay to apply power to terminal L of the Wiper Motor: The wipers operate in lo speed. When the washer button is released, wipe cycles are provided to dry the windshield. The wipers then return to OFF or INT operation.

Lo (or Hi) Speed Wiper Operation

When the Wiper switch is in the LO (or HI) position, section A of the Wiper Switch powers the Interval Override input to the Electronic Switch. The Governor Relay is always pulled in. Wiper Motor current then flows through the Wiper Circuit Breaker and the energized contacts of the Governor Relay to terminal L of the Wiper Motor. HI speed power is applied to the H terminal of the Wiper Motor through section B of the Wiper Switch.

Interval Wiper Operation

During interval operation, the wipers make single wipes at low speed separated by a variable length pause.

When first switch to the INT position, the Interval Timer momentarily closes the Electronic Switch, energizing the Governor Relay. Current flows to the Wiper Motor terminal L, through the energized contacts of the Governor Relay. Ground is connected to terminal C of the Wiper Motor.

As the Wiper Motor turns, the Wiper Motor Switch changes from the grounded PARK position to the hot RUN position. Current now flows through the 63 (R) wire, RUN contact of the Wiper Motor Switch, and resets the Interval Timer, opening the Electronic Switch. The current path continues through the normally closed Governor Relay contact to terminal L of the Wiper Motor. Wiping continues until one wipe is completed. The Wiper Motor Switch returns to the PARK position, power is removed, and the Wiper Motor stops. After a pause (controlled by the variable resistor), the Interval Timer pulls in the Governor Relay to start another wipe.

Braking occurs when the Wiper Motor Switch moves to the PARK position. Wiper Motor terminal L is grounded through the PARK contact of the Wiper Motor Switch and the deenergized contact of the Governor Relay.