TM 5-3805-281-24-1
Sub-System Diagnostics
WINDSHIELD WIPER AND WASHER CIRCUIT THEORY OF OPERATION
terminals 27 and 28, and windshield wiper motor M3 is
The windshield wiper and washer circuit has four
started in the same manner as described for
modes of operation: windshield wiper ON (continuous),
continuous operation. After 1 to 2 seconds, the ground
windshield wiper INT (intermittent), windshield wiper
at terminal 28 of the monitor controller and display is
OFF (park), and windshield wash. The operation of the
removed by the controller, causing motor ground and
windshield wiper and washer circuit is controlled by
intermittent relay K6 to de-energize. However, ground
signals from the monitor controller and the state of the
to wiper motor terminal E is now provided from wiper
wiper motor internal position status switch.
motor terminal S through contacts 3 and 4 of
de-energized relay K6, and the wiper motor continues
WINDSHIELD WIPER CONTINUOUS OPERATION
to run.
When wiper speed switch S9 is placed in the ON
When the wiper motor reaches the intermittent stop
position, windshield wiper relays K6 (motor ground and
position (wiper blade at right side of window), terminal
intermittent), K7 (wiper run), and K8 (hold for park) are
S (which is applied to wiper motor terminal E through
energized by grounds at terminals 26 and 27 of
9015
contacts 3 and 4 of de-energized relay K6) is switched
monitor controller and display A5. Windshield wiper
15
from ground to +24 volts (from motor terminal B) by
relay K9 (motor ground for park) is de-energized by an
24
the wiper motor internal switch. With +24 volts now at
open at terminal 24 of the monitor controller and
both wiper motor terminals, E and L, the motor stops
display.
running. After a few seconds, the cycle is repeated by
another 1 to 2 second ground pulse from terminal 28
Power for windshield wiper motor M3 is supplied from
of the monitor controller and display.
windshield wiper 10-amp fuse F12 through contacts 3
and 5 of energized wiper run relay K7 to terminal L of
WINDSHIELD WIPER PARK OPERATION
the wiper motor. Terminal E of the wiper motor is
connected to frame ground through contacts 3 and 5
When wiper speed switch S9 is turned to the OFF
of relay K6, and the wiper motor runs. The wiper motor
position, monitor controller and display A5 grounds
drives a Pittman arm assembly which moves the wiper
terminal 24, energizing motor ground for park relay K9,
blade back and forth across the windshield.
and opens terminals 26, 27, and 28. If the wiper motor
is running (not in the intermittent stop position), ground
Windshield wiper motor suppression diodes V6 and V7
from terminal S of the wiper motor (applied through
protect the circuit components from voltage transients
relay K8 contacts 3 and 5) keeps windshield wiper
generated by the wiper motor.
relays K7 (wiper run) and K8 (hold for park) energized.
The ground from terminal S is also supplied through
WINDSHIELD WIPER INTERMITTENT OPERATION
the de-energized contacts of motor ground and
intermittent relay K6 to wiper motor terminal E, and the
When wiper speed switch S9 is placed in the INT
wiper motor continues running.
position, monitor controller and display A5 grounds
Continued on next page
CED,OUOE012,7
1921OCT981/2
