INTERVAL WIPER WASHER CIRCUIT WORKS
From 1989 EVTM
HOW THE CIRCUIT WORKS
The Interval Wiper/Washer allows the driver to select LO speed, HI speed or Interval wipe. With the wipers in the interval position, wipes are spaced two to ten seconds apart.
The Interval Wiper/Washer Switch has a momentary Washer Switch, a four-position Wiper Switch and a Variable Resistor which sets interval time.
Pushing the wiper/washer control knob sends current from Fuse 2 through the Washer Switch to the Washer Pump.
LO/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 so that the Electronic Switch and the Governor Relay are pulled in continuously. Wiper Motor current then flows through Fuse 2 and the energized Governor Relay contacts to the L terminal of the Wiper Motor. Power is applied to the H terminal of the Wiper Motor through section B of the Wiper Switch for HI speed operation.
Interval Wiper Operation
During interval operation, the wipers makes single wipes at lo speed separated by a variable length pause.
When first switched to INT position, section A of the Wiper Switch activates the Interval Timer. The Interval Timer momentarily closes the Electronic Switch, energizing the Governor Relay. Current flows to the wiper motor L terminal through the contacts of the energized 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 R wire. Run contact of the wiper motor switch and resets the interval timer, which opens the electronic switch. The current path continues through the de-energized governor relay contact to the L terminal of the wiper motor. Wiping continues to the completion of one wipe. The wiper motor switch returns to the PARK position contact, 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 takes place when the wiper motor switch moves to the PARK position. The wiper motor L terminal is grounded through the PARK contact of the wiper motor switch and the de-energized contact of the governor relay.