DODGE TRUCK 1993 Service Repair Manual

13 - 4
FRAME
AND
BUMPERS

• • Coil — The electrical component that retracts the
cartridge solenoid.
With power applied, the solenoid retracts and pulls
the poppet valve into the OPEN position.
When power is turned off, the spring forces the so­
lenoid back to its normal, CLOSED position.

SOLENOID
VALVE
A The solenoid valve A cartridge contains a poppet
valve. This valve is normally de-energized in the CLOSED position. When closed, the valve retains
pressure in the lift cylinder. When it is energized (valve opened), it allows the fluid to flow from the
lift cylinder back to the reservoir. This enables the
plow blade to lower via gravity.
Solenoid valve A is designed to remain energized
(valve open) during plowing to provide a floating
blade position. This ensures that the plow blade is guided up-down by the surface deviations.

SOLENOID
VALVE
B The solenoid valve B cartridge contains a spool
valve. This valve is normally in the de-energized CLOSED position. This allows the fluid to flow to the
C solenoid. In the energized OPEN position, the fluid
is diverted to the lift cylinder. This causes the plow
blade to be raised.

SOLENOID
VALVE
C The solenoid valve C cartridge contains a spool
valve that is normally in the de-energized CLOSED
position. This allows the fluid to flow to the right- side power angling cylinder. This angles the blade to
the left. At the same time, it allows the fluid from
the retracting left-side power angling cylinder to re­
turn to the pump reservoir. Energizing the solenoid valve will route fluid to
the left side angling cylinder. This angles the plow
blade to the right. Also, the fluid is forced from the
retracting right side cylinder. It flows through the C cartridge valve and returns to the pump reservoir.
MECHANICAL HYDRAULIC VALVES The mechanical hydraulic valves all have the same
function: they control the direction of the hydraulic
fluid flow.

CHECK
VALVES
Check valves allow fluid to flow freely in one direc­
tion while preventing fluid from flowing in the oppo­ site direction.
A pump check valve is used to prevent fluid from
leaking back through the pump to the reservoir.
Two additional check valves are necessary because
solenoid valves B and C have some leakage.
One check valve is located between solenoid valve
B and the lift cylinder. It prevents fluid in the lift cylinder from leaking back through solenoid valve B.
If fluid leaks back, it could angle the blade to the
left. This would force fluid through solenoid valve C into the right side cylinder.
The other check valve is located between valve B
and valve C. It prevents fluid from being forced
through solenoid valve B.

PILOT CHECK VALVE
A pilot check valve has a piston in addition to a
ball seat and spring. A pilot check valve is located
between solenoid valve C and the reservoir. It has two functions:
• Prevents the hydraulic fluid in either angling cyl­inder from leaking back to the reservoir.
• Allows the hydraulic fluid from a retracting an­
gling cylinder to return to the reservoir. The valve action is done by fluid moving the pis­
ton, which forces the check ball off its seat.

CROSSOVER
RELIEF VALVE
This valve protects against damage by a sudden
impact against the end of the blade. This will cause
high hydraulic pressure to accumulate in one of the angling cylinders. The hydraulic pressure increases enough to open
the crossover relief valve. The valve allows the
highly pressurized hydraulic fluid to flow to the other cylinder. This cushions the impact and changes
the position of the blade.
SYSTEM OPERATION Refer to Figures 2 through 5 for voltage application
and hydraulic fluid flow for each snow plow function.
Each figure shows the components that are actuated
for each function.

SNOW
PLOW WIRING DIAGRAMS
Refer to Figures 6, 7 and 8 for wiring diagrams.
Refer to Specifications chart at the end of this
group.

SNOW PLOW MALFUNCTION DIAGNOSIS
AND

TESTS
Refer to the charts and illustrations for proper di­
agnosis.
SOLENOID VALVE COIL FUNCTIONAL TEST Test the coils for proper operation, according to the
following procedure. (1) Hold a screwdriver blade about 1/8 inch above
the nut on the coil to be tested. (2) Have a helper operate the control switch that
energizes the applicable coil.

CAUTION:
Do not connect an ohmmeter to a coil
when it is
applied.
This
can
cause
internal
damage
to the ohmmeter.
(3) If the coil is working, the electromagnetic ac­
tion will pull the screwdriver down to the retaining nut. If this does not occur, use an ohmmeter to check
the coil for continuity.

FRAME
AND
BUMPERS
13 -

TAN-

BLACK*
-o

ORANGE
WITH

WHITE

TRACER

SWITCH
I
RAISE

| AND j
!
LOWER
x

RED-
6 o

SWITCH

O
IGNITION SWITCH

ANGLE

TAN
LIGHT

'GREEN
ORANGE

WITH

WHITE
TRACER
FUSE

»
+
BATTERY

•o

SOLENOID SWITCH

•
MOTOR

ENERGIZED:
MOTOR
AND "B"
COIL
PRESSURE
RELIEF
"B"
SOLENOID

JUL.
'C"
SOLENOID
ANGLING CYLINDER

CSSE]
OPERATING
PRESSURE
EXHAUST
INTAKE
OR
DRAIN

METERED
FLOW

RB525

Fig.
2 Raise Blade—Voltage Application & Hydraulic Fluid Flow

- 6 FRAME AND BUMPERS
•
SWITCH TAN

ORANGE
WITH

WHITE

TRACER

RED
N 6
o IGNITION SWITCH
_L_
ANGLE

ORANGE
WITH
WHITE TRACER L f
FUSE

LIGHT GREEN

u==c

SOLENOID SWITCH >+
BATTERY
•o

ENERGIZED:
"A" COIL C" SOLENOID
POWER
ANGLING CYLINDER
LOWER AND FLOAT
(FORCE APPLIED AGAINST
LIFT
RAM)
OPERATING
PRESSURE
EXHAUST
INTAKE OR DRAIN

METERED
FLOW

RB526

Fig. 3
Lower
&
Float
Blade—Voltage
Application
&
Hydraulic
Fluid
Flow

FRAME
AND
BUMPERS
13 - 7

IGNITION
SWITCH
L

BLACK

mm OPERATING PRESSURE EXHAUST
^SS3 INTAKE OR
DRAIN
METERED
FLOW

RB527
Fig, 4 Angle Blade Right-Voltage Application & Hydraulic Fluid Flow

13 - 8
FRAME
AND
BUMPERS

TAN
IGNITION SWITCH

BLACK

WSSm
OPERATING
PRESSURE

mm
EXHAUST

ESBS3 INTAKE
OR
DRAIN
METERED
FLOW

J9001-1
Fig. 5 Angle Blade Left—Voltage Application & Hydraulic Fluid Flow

•

FRAME
AND
1UMPERS
-13 - S
SNOW
PLOW
DIAGNOSIS

Condition
Possible
Coys®
Correction

PLOW
BLADE
WILL NOT LIFT OR
LIFTS
SLOWLY

PLOW
BLADE
WILL
NOT
ANGLE
RIGHT-

MOTOR
IS
OPERATIONAL

PLOW
BLADE
WILL NOT
ANGLE
LEFT-

MOTOR
IS
OPERATIONAL

PLOW
BLADE
WILL NOT
ANGLE-

MOTOR
IS
OPERATIONAL

PLOW
WILL NOT
REMAIN
IN

ANGLED
POSITION

MOTOR
DOES
NOT
OPERATE

PLOW
BLADE
WILL NOT
LOWER

PLOW
BLADE
CREEPS
DOWNWARD

PLOW
BLADE
WILL NOT

CLEAN
SURFACE

BLADE
WILL NOT
FOLLOW

SURFACE
DEVIATIONS

SNOW
STICKS
TO
FACE

OF
BLADE
(n)
Low hydraulic fluid level.
(b) Discharged
battery.

(c) Leaking or open "A" cartridge.
(d) No voltage at
"B"
coil.
(e) Inoperative
"B"
coil.
(f) Malfunctioning motor.
(g) Malfunctioning pump.
(a) Improper coupler engagement.
(b) Mechanical bind or
interference.

(c) Malfunctioning coupler.
(d) No voltage at
"C"
coil.
(e) Inoperative "C" coil.
(f) Inoperative
"C"
cartridge.
(a) Improper coupler engagement.
(b) Mechanical bind or
interference.

(c) Malfunctioning coupler.
(d) Leaking or open crossover
relief
valve.
(a) Improper coupler engagement. (b) Mechanical bind or
interference.

(c) Leaking or open crossover
relief
valve.
(a) Air in cylinders and
hoses.

(b) Leaking
"C"
cartridge O-ring
seals.

(c) Leaking or open pilot check valve.
(d) Leaking crossover
relief
valve.
(e)
Crossover
relief
valve opening
pressure too low.
(a) Discharged or
defective
battery.

(b)
Loose
or corroded
electrical
connections.

(c) Inoperative solenoid switch.
(d) Malfunctioning control switch.
(e) Malfunctioning motor.
(a) No voltage at "A" coil.

(b)
"A" cartridge jammed in closed
position.

(c) Inoperative "A" coil.
(a) Leaking "A" cartridge.
(b) Leaking "A" cartridge O-ring seal.
(c) Leaking B-Check Valve.
(d) Leaking Ram Packing Cup.
(e) Leaking O-ring seal at bottom of cylinder.
(a) Runner height incorrect. (b) Cutting edge unevenly worn.
(a) Not in "Lower Float Position".
(b) Insufficient slack in
lift
chain.
(a)
Sno-Flo
paint worn off. (a) Add fluid to proper level.
(b) Recharge
battery.

(c) Clean or replace "A" cartridge.
(d) Locate malfunction and
repair.

(e) Replace
"B"
coil.
(f) Repair or replace motor. (g) Replace pump.
(a)
Engage
coupler properly.
(b) Eliminate mechanical bind or
interference.

(c) Repair or replace coupler.
(d) Locate malfunction and
repair.

(e) Replace
"C"
coil.
(f) Clean or replace
"C"
cartridge.
(a)
Engage
coupler properly.
(b) Eliminate mechanical bind or
interference.

(c) Repair or replace coupler.
(d) Clean or replace crossover
relief
valve.
(a)
Engage
coupler properly.
(b) Eliminate mechanical bind or
interference.

(c) Clean or replace crossover
relief
valve.
(a) Purge cylinders and
hoses.

(b) Replace O-ring
seals.

(c) Clean or replace pilot check valve.
(d) Clean or replace crossover
relief
valve.
(e) Replace crossover
relief
valve.
(a) Recharge or replace
battery.

(b) Clean and tighten
electrical
connections.

(c) Replace solenoid switch.
(d) Replace control switch.
(e) Repair or replace motor.
(a) Locate malfunction and
repair.

(b) Clean or replace "A" cartridge.
(c) Replace "A" coil.
(a) Clean or replace "A" cartridge.
(b) Replace O-ring seal.
(c) Clean or replace Pump Check Valve.
(d) Replace Ram Packing Cup.
(e) Replace O-ring seal.
(a) Adjust runners.
(b) Replace.
(a) Position switch at "Lower Float"
(b) Adjust
lift
chain.
(a) Refinish.
J9001-3

13
- 10
FRAME
AND
BUMPERS

TO TURN

SIGNAL
FLASHER
<
(SEE
SHEET
27) y -Dl 18RD/YL*
FUSE
#5
(20 AMP) Dl
18RD
YL*
-Dl 18RD/YL*
-Dl 18RD/YL*- Dl 18RD/YL*
TO R.W.A.L.
j MODULE
(SEE
SH
51, 53)

BLACK
TO

IGNITION
SWITCH

(SEE
SH
10)

-SP4
18WT/BR*

PLOW

CONTROL
SWITCH

UP
& DOWN L.

-SP4
18WT/BR*-

-SP4
18WT/BR*-
PLOW

CONTROL
SWITCH
LEFT
TO
RIGHT

-SP4
18WT/BR* -Dl 18RD/YL*-

TRANSMISSION
OIL

TEMPERATURE
LAMP
-SP4
18WT/BR*-

-SP4
18WT/BR*

-SP4
18WT/BR*

-SP1
18WT/BK* I Dl 18RD/YL*

-SP3
18 WT/RD*

-SP3
18WT/RD*-

-SP1
18WT/BK*-
SP4
18WT/BR* I

SP4
18WT/BR* !

-SP4
18WT/BR* j
—Dl 18RD/YL*

-SP5
18WT/LG* I
-SP5
18WT/LG*-
-T2 18LG/RD*-
8901-3

Fig. 6 Snow Plow
Control
Wiring
Diagram

SNOW PLOW DOWN
SOLENOID
(FRONT

SNOW
PLOW
FRAME)
SNOW PLOW
RIGHT SOLENOID
(FRONT
SNOW PLOW FRAME)
TRANSMISSION
OIL

TEMPERATURE LAMP TRANSMISSION
OIL

TEMPERATURE SWITCH
(RIGHT
SIDE
BELOW RADIATOR)
8901-4

Fig.
7
Snow
Plow Control Wiring Diagram (Cont'd)

13
- 12
FRAME AND BUMPERS
TO FRONT

END
WIRING
(SEE
SH
21)

T
T
18BK
18BK

YL* TO HEADLAMP
Jr

SWITCH -L2
14LG
TO FRONT
END
WIRING
(SEE
SH
22)

BLACK (RIGHT
SIDE

RADIATOR
YOKE

PANEL) BLACK
(RIGHT
' UPPER
SNOW
PLOW

FRAME)

BLACK

LEFT
AUXILIARY
PARK AND
TURN
SIGNAL LAMP
LEFT
AUXILIARY
HEADLAMP
RIGHT
AUXILIARY
HEADLAMP
RIGHT
AUXILIARY
PARK AND
TURN
SIGNAL LAMP
8901-2
Fig. 8
Snow
Plow
Auxiliary
Lighting Wiring Diagram

•

FRAME
AND
BUMPERS
13 - 13
POWER
UNIT

DISASSEMBL
Y/INSPECTION
(1) Remove the drain plug (Fig. 9). Drain the unit.
(2) Extend the ram and piston rod completely.
Drain the remaining oil from the cylinder.
(3) Remove the cover locknuts (Fig. 9). Remove the
cover.
(4) Inspect the casting for damage and cracks. In­
spect the seal for cuts (Fig. 9).
(5) Remove the ram and the piston. Inspect the ny­
lon sleeve, the piston, and the piston follower for ex­ cessive wear (Fig. 10).
(6) Inspect the cylinder for pitting and scoring in
the bore (Fig. 10).
(7) Inspect the ram for nicks, scratches, and corro­
sion (Fig. 10).
(8) Inspect the piston packing cup for wear (Fig.

10).

(9) Clean and inspect the base strainer.
(10) Replace all the O-ring seals during assembly.
(11) Loosen the motor bolts. Do not remove the
bolts from the motor. Retain the motor end plate dur­ ing removal. Temporarily install two
1/4-20
nuts on
the motor bolts to retain the motor intact.
Both Prestolite and American Bosch motors
are used in snow plow power units. A Prestolite
motor can be identified by a domed top cover and the trade name stamped on the body. Amer­
ican Bosch motors have a flat top cover and no
identifying name or marks. (12) Remove the pump drive shaft seal.
(13) Verify the seal kit components are correct for
the unit. (14) Dip the new seal in oil. Install it over the
pump shaft with the seal lip facing down. (15) Position the seal in the pump housing slightly
below the boss face. (16) Remove solenoid valve A coil from the base.
Test it for continuity. The normal coil DC resistance is 9.0 ohms ±10%. (17) Remove solenoid valve A cartridge with a 1
and
1/8-inch
diameter deep socket wrench. Inspect
for external damage. (18) Remove the filters. Clean the screens with
cleaning solvent and compressed air. Discard the O-ring seals and the nylon retaining rings. (19) Remove the pump housing (Fig. 9). Remove
the insert valve, the ball, the spring, and the re­
tainer from the pump housing (Fig. 11). Inspect all the components for damage and contamination. Dis­
card the O-ring seals. (20) Remove the socket-head screws. Remove the
valve block from the pump housing (Fig. 9). Discard
the O-ring seals. (21) Remove solenoid valve B with special tool
J-25399 (Fig. 9). (22) Remove the ball and spring from the valve
block (Fig. 9). Clean the solenoid valve. Inspect it for external damage. (23) Disassemble the three-way valve (Fig. 9). Dis­
card the O-ring seal. (24) Remove and clean solenoid valve C with spe­
cial tool J-25399 (Fig. 9). Inspect the solenoid valve
for external damage.
(25) Disassemble the four-way valve (Fig. 12). Dis­
card the O-ring seals (Fig. 12). (26) Test solenoid valve B and C coils for electrical
continuity. The normal coil DC resistance is 3.7

ohms.
(27) Remove the pilot check valve plug, the spring
and the ball from the bottom of the valve block. (28) Inspect the spring for damage and the ball
seat for nicks. (29) Remove the acorn nut for access to the cross­
over valve components (Fig. 9).
(30) Remove the crossover valve components (Fig.

13).
Inspect for external damage. Discard the O-ring

seals.
(31) Clean the block with compressed air to re­
move all foreign material.

ASSEMBLY
Verify that all components are thoroughly clean
and free of foreign material. Use replacement gas­
kets and seals during assembly. Petroleum jelly should used for installing the rubber O-ring seals.
(1) Install the crossover valve components in the
valve block with replacement O-ring seals (Fig. 13) (2) Install the ball, spring and pressure plug with
a replacement O-ring seal in the bottom of the valve
block (Fig. 13) (3) Assemble solenoid valve C with replacement
O-ring seals and nylon retainer rings (Fig. 12). (4) Install solenoid valve C with Tool J-25399 (Fig.

9).
(5) Assemble solenoid valve B with replacement
O-ring seals.
(6) Install the ball, spring and solenoid valve B
with Tool J-25399 (Fig. 9). (7) Install the valve block and the replacement
O-ring seals on the pump base. (8) Install the retainer, the spring, the ball, the in­
sert valve and the pump housing with replacement
O-ring seals (Fig. 11). Tighten the pump housing
base nuts to 11.3 N*m (100 in. lbs.) torque. (9) Install the filters and the plugs with replace­
ment O-ring seals (Fig. 9). (10) Install solenoid valve A cartridge in the pump
base with replacement O-ring seals (Fig. 9). (11) Install solenoid valve A coil (Fig. 9).
(12) Install the motor on the pump housing (Fig.

9).
Engage the gear shaft tang with the notch in the
motor output shaft. Tighten the motor housing cap- screws to 5 N#m (45 in. lbs.) torque. (13) Install the ram and piston with replacement
O-ring seals (Fig. 9). (14) Position the cover on the reservoir. Secure it
with locknuts (Fig. 9). Tighten the locknuts to 11.3 Nrn (100 in. lbs.) torque.