Rectangular Motor

Fig. 1 Rectangular windshield wiper motor. Shown w/washer pump installed:

Fig. 2 Rectangular windshield wiper motor electrical connections:

The rectangular motor, Fig. 1, consists of an armature, brush plate assembly, field coils and a housing which is attached to a gear housing. The motor electrical connections, park switch, and on some models a washer pump are also mounted on the gearbox. A gear on the commutator end of the armature drives an intermediate gear and pinion assembly, which in turn drives the output shaft. A crank arm on the output shaft operates wipers through a pivot link (transmission) assembly.
When ignition is on, battery voltage is supplied to motor terminal 2, Fig. 2. Current flows through the series field to a splice where it is divided, and part passes through the armature and part through the shunt field. The armature and shunt field circuits are completed to ground through the wiper switch, with motor speeds determined by resistance in the shunt field ground path.
Placing wiper switch in low position, grounds motor terminals 1 and 3, Fig. 2, at the wiper switch. Shunt field current flows directly to ground through terminal 3, armature current flows to ground through terminal 1 and the motor runs at low speed. Placing wiper switch in high position grounds terminal 1, but terminal 3 remains open. Armature current flows directly to ground through terminal 1, shunt field current flows to ground through a resistor connected between terminals 1 and 3, and the motor runs at high speed due to the weakened shunt field.
When wiper switch is turned off, and wipers are not in park position, terminal 1 is grounded through the closed motor park switch contacts. Terminals 1 and 3 are connected through the wiper switch, and the motor runs at low speed. When wipers reach their lowest point of travel, a cam on the motor output shaft opens the park switch, and the motor stops.
On models with pulse wipers, a pulse control module provides a delay wipe mode through the low speed circuit. When wiper control is in delay position, battery voltage is supplied to a capacitor in the module through a variable resistor. When the capacitor is fully charged, it activates a switching circuit which provides a ground to begin wiper operation. As the motor operates, park switch contacts close, the capacitor discharges, and the motor ground is maintained through the park switch. When wipers complete their cycle, the park switch opens and the capacitor begins to recharge. Delay between wipe cycles is determined by a variable resistor, which controls charging current to the capacitor. Higher resistance produces a longer delay.