Firebird V8-305 5.0L (1982)
Fig. 6 Gear box relay and drive gear assembly, shown out of park position. Compound wound round windshield wiper motor
Fig. 7 Gear box relay and drive gear assembly, shown in park position. Compound wound round windshield wiper motor
Operation:
When ignition is on, battery voltage is supplied to gear box 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 gear box 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, or medium position on Cadillac, 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. Medium speed on Cadillac models results from a 13 ohm resistor in the wiper switch, wired parallel with
the gear box relay resistor, which produces approximately 8 ohms resistance in the shunt field circuit.
Placing wiper switch in off position opens the circuit to the gear box 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 gear box relay and allows wipers to move below their lowest point of normal
travel. The drive pawl pushes the latch arm against the gear box relay contacts, opening the contacts and stopping the motor in park position, Fig. 7.
Multiplex Pulse Wiper
