Seville V8-273 4.5L (1989)
Fig. 5 Compound Wound Round Windshield Wiper Motor W/multiplex Pulse System
ROUND MOTOR
The 4 or 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. Both standard and pulse motors used on Corvette have an additional ground lead to ground the motor housing to the wiper switch.
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, 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 gearbox relay resistor, which produces approximately 8 ohms resistance in the shunt field circuit.
Fig. 6 Gearbox Relay And Drive Gear Assembly, Shown Out Of Park Position. Compound Wound Round Windshield Wiper Motor
