This schematic here is the high speed windshield and washer wiring diagram for the 1959 Chevrolet cars. In high speed, the shunt winding lead is open-circuited at the dash, causing the winding to ground through a resistor at the motor. This decreases current flow through the shunt winding, and increases flow through the series winding, thus increasing motor speed. Components shown inside are: dash control, shunt field, series field, relay, switch, power supply from the battery, etc. Click on image to view it larger in a new tab.