Round Motor

Fig. 3 Two speed round windshield wiper motor:

Fig. 4 Modified pulse windshield wiper motor:

Fig. 5 Multiplex pulse windshield wiper motor:

The 4-1/2 inch long, round motor assembly consists of an armature, field coil and end cap assembly, and a brush plate which fits over the armature and is connected to the field coils. The motor assembly is attached to a gearbox housing which also provides a mount for the washer pump. A worm gear on the armature commutator end drives the output shaft at a 90° angle through a drive gear and pawl assembly.
The gearbox assembly contains a magnet switch, relay and terminal board assembly (gearbox relay) which provides electrical connections and controls current flow through the motor. On standard (non-pulse) motors, Fig. 3, the two motor leads to the gearbox relay are concealed and routed through a cavity in the gear housing. On pulse type motors, Figs. 4 and 5, the two motor leads to the gearbox relay, and the feed wire to the pulse relay are exposed.

Fig. 3 Two speed round windshield wiper motor:

Fig. 6 Gearbox relay & drive gear assembly. Shown out of park position:

Fig. 7 Gearbox relay & drive gear assembly. Shown in park position:

STANDARD (NON-PULSE) WIPER OPERATION
When ignition is on, battery voltage is supplied to gearbox relay terminal 2, Fig. 3. When terminal 1 is grounded, relay contacts close and current is supplied to the motor. Current flows through the series field to a splice where it is divided, and part passes through the armature to the motor housing ground, and part through the shunt field. Motor speeds are determined by the amount of current flowing through the shunt field.
Placing wiper switch in low position grounds gearbox relay terminals 1 and 3. The relay contacts close, shunt field current flows directly to ground at the switch through terminal 3, and the motor runs at low speed. Placing wiper switch in high grounds relay terminal 1, but terminal 3 remains open. Shunt field current flows to ground through a 20 ohm resistor connected between terminals 1 and 3, and the motor runs at a higher speed due to the weakened shunt field.
Placing wiper switch in off position opens the circuit to the gearbox relay magnet switch. This allows a spring loaded arm to move into the path of the output gear drive pawl, Fig. 6, while relay contacts remain closed. The shunt field is grounded through the wiper switch and the motor operates at low speed, allowing the gear mechanism to park the wipers and stop the motor.
As the output gear rotates, the drive pawl engages the latch arm on the gear box relay, and the output gear is unlocked from the drive pawl, lock pawl and drive plate. Since the output shaft and gear shaft are off center, continuing rotation causes a cam action which moves the drive pawl into a slot in the gearbox relay and allows wipers to move below their lowest point of normal travel. The drive pawl pushes the latch arm against the gearbox relay contacts, opening the contacts and stopping the motor in park position, Fig. 7.



PULSE WIPER OPERATION
Modified Pulse System
Models equipped with pulse wipers use a motor similar to the one used on standard wiper systems which has been modified to provide a delay wipe mode. In addition to standard wiper system components, the modified pulse system includes a voltage feed circuit to the wiper switch and a variable resistor in the switch, a pulse relay and holding switch mounted on the washer pump, and a timer circuit. The timer circuit, consisting of a capacitor, transistor and two diodes, is mounted in the washer pump or contained in a separate module.
The gearbox relay functions in a similar manner on both standard and pulse systems, but on pulse systems the gearbox relay supplies voltage to the pulse relay which controls current flow to the motor windings. In all wiper switch positions except delay, the gearbox and pulse relays are grounded simultaneously through the wiper switch, and the motor operates as outlined in ``Standard (Non-Pulse) Wiper Operation.'' When wiper switch is in delay position, pulse relay operation is controlled by the timer circuit.
Placing wiper switch in delay position grounds gearbox relay terminals 1 (relay) and 3 (shunt field) at the switch, and battery voltage is supplied to the timer circuit capacitor through the variable resistor in the switch. When the capacitor is fully charged, it activates the timer transistor. The transistor completes the pulse relay ground circuit, and current flows through the motor windings. As the motor begins to operate, holding switch contacts close, the capacitor discharges partially, and the pulse relay ground is maintained through the holding switch. As wipers complete their cycle, a fin on the washer pump drive cam opens the holding switch, Fig. 8. This stops the motor and allows the timer capacitor to recharge.
This cycle repeats as long as wiper switch is in delay position. Delay between wipe cycles is determined by controlling charging current to the capacitor through the switch resistor. Higher resistance produces longer delay.

Fig. 8 Pulse wiper system holding switch contacts:

Multiplex Wiper System
Models with pulse wiper use a motor similar to the one used on standard systems, but with modifications to provide a delay wipe mode. The multiplex system, while similar to earlier pulse wiper systems, uses an integrated circuit timer and the voltage feed to the wiper switch has been eliminated. In addition to standard wiper system components, the multiplex system uses a variable resistor in the wiper switch, a pulse relay and holding switch mounted in the washer pump, and a timer circuit. The timer, consisting of a capacitor and integrated circuit, is mounted on a circuit board in the washer pump or contained in a separate module.
The gearbox relay functions in a similar manner on both standard and multiplex systems. However, on pulse systems the gearbox relay supplies voltage to the pulse relay, current to the motor windings is controlled by the pulse relay, and voltage is supplied to the timer circuit from motor terminal 2. In all switch positions except delay, the gearbox relay, pulse relay and timer capacitor circuits are completed directly to ground through the wiper switch. This deactivates the timer circuit and allows the motor to operate as outlined in ``Standard (Non-Pulse) Wiper Operation.''
Placing wiper switch in delay position grounds gearbox relay terminals 1 (relay) and 3 (shunt field), and the timer capacitor is partially grounded through the variable resistor, allowing it to charge at a controlled rate. When the timer capacitor is fully charged it activates the integrated circuit. The integrated circuit completes the pulse relay ground circuit, and current flows through the motor windings.
As the motor begins to operate, holding switch contacts close, the capacitor discharges partially, and the pulse relay ground is maintained by the holding switch. As wipers complete their cycle, a fin on the washer pump drive cam opens the holding switch, Fig. 8, wipers stop and the timer capacitor begins to recharge. This cycle repeats as long as wiper switch is in delay position. Delay between wipes is determined by varying resistance between the timer capacitor and ground.