GMC 4000 Series Service Manual page 33

Sec. 1
Page 26
GENERAL MAINTENANCE
Series W in d in g Shunt W in d in g
lGr
i— ' r f
r - f < 7 |— IR T — I
t
nturp — *
Battery A rm a tu re
L O W SPEED C IRC U ITS
Series W in d in g S h u n t^ W in d in g
( G ra y
-W
2 4 O H M
L ^ p
Battery A rm a tu re
a tu rp — ■ *
H IG H SPEED C IRC U ITS
Figure 10— H igh-Low Speed Circuits
Wiper Inoperative
1. Check wiring harness connections at motor
and at dash switch.
2. Check fuse (if used) or circuit breaker.
3. See if wiper motor ground strap is secure.
4. Check for loosely mounted dash switch.
5. If wiper still fails to operate, disconnect
wiring from motor, and check for 12 volts at motor
No. 2 terminal (fig. 11). No voltage indicates de­
fective wiring.
6. With harness disconnected from motor, try
operating motor as shown in figure 11. If wiper fails
to operate, remove wiper transm ission linkage and
recheck wiper operation. If wiper operates, linkage
is at fault. If wiper does not operate, remove unit
from vehicle for disassembly.
Wiper Has One Speed - Fast
Check for a defective dash switch or open lead
between motor No. 3 terminal and dash switch.
Wiper Has One Speed (LOW) and Shuts Off
With Dash Switch in ''HIGH" Speed Position
Reverse harness leads that connect to motor
terminals Nos. 1 and 3.
Blades Do Not Return to "PARK" Position
When Wiper is Turned Off
1. Check wiper motor ground connection to the
cab.
2. Remove wiper motor from cab and check
for dirty, bent or broken "PARK" switch contacts.
Wiper Speed Normal in "LOW"
But Too Fast in "HIGH"
Remove wiper motor from cab and check for
an open motor resistor.
G M C S E R V I C E M A N U A L
2 4 O H M
Resistor
| i \ _ v
Park Sw itch
D a sh Sw itch
Resistor
NOTE: Terminals Are Numbered
For Purposes of Explanation
LO SPEED—As Shown
HI SPEED—Disconnect Jumper Wire
From Terminal No. 3
OFF—Leave Jumper Connected to
Terminals 1 and 3 But Disconnect
it From Ground
Figure 1 1 — Troubleshooting Wiper Motor Circuit
Intermittent Operation
Check for loose wiper ground connection and/
or loose dash switch mounting.
WIPER M OTOR A N D GEAR B O X
DISASSEMBLY A N D ASSEMBLY
DISASSEMBLY (Fig. 12)
Gear Box
1. Remove washer pump mounting screws and
lift pump from motor.
2. Remove washer pump drive cam (fig. 16).
Cam is pressed on shaft but may be removed by
carefully wedging two screwdrivers between cam
and plate.
3. Lightly clamp crank arm in a vise and re­
move crank arm retaining nut. Separate arm from
shaft.
NOTE: Failure to clamp crank arm may re­
sult in stripping of drive gears when retaining nut
is removed.
4. Remove seal cap, retaining ring, and end-
play washers.
5. Drill out gear box cover attaching rivets
and remove cover from motor assembly.
NOTE: Necessary parts for reassembly of
gear box cover to motor is contained in service
repair package.
6. Remove output gear and shaft assembly,
then slide intermediate gear and pinion assembly
off shaft. Note position of wave washers.
7. If necessary, remove terminal board and
"PARK" switch by marking wires and unsoldering
at terminal lugs. Drill out terminal board attaching
rivets and remove board.
Jum per W ire
For Bench Testing
l>
Connect to
W ip e r H ou sin g
A m m eter
T-030