Mercedes-Benz Sprinter / Dodge Sprinter. Service manual — part 254

CHECK VALVE

DESCRIPTION

A single washer system check valve is standard

equipment on this model, and is installed in the
washer system plumbing (Fig. 4). The check valve is
integral to the washer plumbing fitting located on
the underside of the cowl top panel behind the rear
of the hood panel opening in the engine compart-
ment. The check valve consists of a molded plastic
body with three barbed hose nipples, one at the inlet
side of the valve body and two at the outlet side. The
check valve cannot be adjusted or repaired and, if
faulty or damaged, it must be replaced.

OPERATION

The check valve provides more than one function

in this application. It serves as a plumbing connector
fitting between the engine compartment and washer
nozzle sections of the washer supply hose. It prevents
washer fluid from draining out of the washer supply
hoses back to the washer reservoir. This drain-back
would result in a lengthy delay from when the
washer switch is actuated until washer fluid was dis-
pensed through the washer nozzles, because the
washer pump would have to refill the washer plumb-
ing from the reservoir to the nozzles. Such a drain-
back condition could also result in water, dirt, or
other outside contaminants being siphoned into the
washer system through the washer nozzle orifice.
This water could subsequently freeze and plug the
nozzle, while other contaminants could interfere with
proper nozzle operation and cause improper nozzle
spray patterns. In addition, the check valve prevents
washer fluid from siphoning through the washer noz-
zles after the washer system is turned Off.

When the washer pump pressurizes and pumps

washer fluid from the reservoir through the washer
plumbing, the fluid pressure unseats a diaphragm
from over a sump well within the valve by overriding

the spring pressure applied to it by a piston. With
the diaphragm unseated, washer fluid is allowed to
flow toward the two washer nozzles. When the
washer pump stops operating, the spring pressure on
the piston seats the diaphragm over the sump well in
the valve and fluid flow in either direction within the
washer plumbing is prevented. The check valve can-
not be adjusted or repaired and, if faulty or damaged,
it must be replaced.

REMOVAL

(1) Unlatch and open the hood panel.
(2) Disconnect the washer hoses from the three

barbed nipples of the check valve unit (Fig. 5).

(3) Remove the check valve unit from the under-

side of the cowl top panel.

INSTALLATION

(1) Position the check valve unit to the underside

of the cowl top panel (Fig. 5).

(2) Reconnect the three washer hoses to the

barbed nipples of the check valve unit.

(3) Close and latch the hood.

Fig. 4 Check Valve

1 - INLET NIPPLE
2 - CHECK VALVE
3 - OUTLET NIPPLE (2)

Fig. 5 Check Valve Remove/Install

1 - COWL HOOD SEAL
2 - CHECK VALVE
3 - HOSE TO WASHER NOZZLE (2)
4 - HOSE FROM WASHER PUMP

VA

WIPERS/WASHERS

8R - 11

RAIN SENSOR

DESCRIPTION

The rain sensor provides the primary input for the

optional automatic wiper system (Fig. 6). The rain
sensor is located on the inside of the windshield,
where it is concealed within the molded plastic trim
cover that snaps over the base of the rear view mir-
ror arm. The sensor fits within the center of a ring-
like molded plastic bracket that is glued to the inside
of the windshield glass and that also serves as the
support for the rear view mirror.

The rain sensor is contained within a circular

molded black plastic housing with a short pigtail
wire and a connector insulator containing three ter-
minal cavities that exits one side of the housing. This
pigtail connects the rain sensor to the vehicle electri-
cal system through a dedicated take out and connec-
tor of the overhead wire harness that extends from
above the headliner. A molded plastic trough routes
and conceals the pigtail wires on the inside of the
windshield between the rear view mirror base and
the headliner.

The windshield side of the rain sensor housing is

open, but covered with a clear gelatin-like material
that protects the internal electronic sensor circuitry
and serves as the lens for the InfraRed (IR) diodes
and photocells within the sensor housing. This gel
coating must never be touched or the rain sensor
function may be impaired and the unit rendered
unusable. The rain sensor cannot be adjusted or
repaired and, if damaged or faulty, the entire sensor
must be replaced. The sensor bracket and a rear view

mirror adhesive kit are available for separate service
replacement.

OPERATION

The rain sensor operates on battery current and a

clean ground received from the rain sensor control
module. The rain sensor contains InfraRed (IR)
diodes that direct IR light beams at the windshield
at an angle. When the windshield glass is dry, most
of this IR light is reflected back to the sensor, which
uses photocell receivers to measure the intensity of
the light. When moisture accumulates on the wind-
shield glass, much of the IR light is refracted away
from the photocell receivers. This causes changes in
the signal output of the rain sensor. The rain sensor
control module monitors the signal output from the
sensor and then controls the wiper motor speed and
wipe intervals accordingly.

It is important to note that the default condition

for the wiper system is automatic wipers Off; there-
fore, if no message is received from the rain sensor
by the rain sensor control module, the automatic wip-
ers will be disabled. If automatic wipers are disabled,
normal low and high speed continuous wiper opera-
tion are unaffected. Also, due to the low voltage
nature of the rain sensor signal and the impact that
minor fluctuations in this signal strength can have
on wiper operation, grounded shielding circuits are
provided at the roof and control module connectors to
control electrical induction into the sensor signal cir-
cuit.

The hard wired rain sensor circuits may be diag-

nosed using conventional diagnostic tools and meth-
ods. However, conventional diagnostic methods may
not prove conclusive in the diagnosis of the internal
circuitry or the optics of the rain sensor. Refer to the
appropriate wiring information.

STANDARD PROCEDURE

RAIN SENSOR BRACKET REPLACEMENT

The rain sensor fits within the center of a ring-like

molded plastic bracket that is glued to the inside of
the windshield glass and that also serves as the sup-
port for the rear view mirror arm. If the bracket
should come loose from the windshield, it must be
reinstalled using a rear view mirror adhesive kit and
the procedure that follows.

Fig. 6 Rain Sensor

1 - HEADLINER
2 - TROUGH
3 - WINDSHIELD
4 - RAIN SENSOR
5 - MIRROR

8R - 12

WIPERS/WASHERS

VA

WARNING: To avoid personal injury or death, on
vehicles equipped with airbags, disable the supple-
mental

restraint

system

before

attempting

any

steering wheel, steering column, airbag, seat belt
tensioner, or instrument panel component diagno-
sis or service. Disconnect and isolate the battery
negative (ground) cable, then wait two minutes for
the system capacitor to discharge before perform-
ing further diagnosis or service. This is the only
sure way to disable the supplemental restraint sys-
tem. Failure to take the proper precautions could
result in accidental airbag deployment.

CAUTION: Do not touch the gel-like surface of the
rain sensor or the sensor function may be impaired
and the sensor rendered unusable.

(1) Disconnect and isolate the battery negative

cable.

(2) Remove the rear view mirror and the rain sen-

sor from the rain sensor bracket. (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/RAIN

SENSOR

-

REMOVAL).

(3) Cut diagonally through the nylon mesh fabric

from the rear view mirror adhesive kit (Fig. 7).

(4) Place the rain sensor bracket onto the nylon

mesh fabric (Fig. 8).

(5) Cut the two sections of nylon mesh fabric to

the contours of the rain sensor.

NOTE: If the early version of the rain sensor
bracket is used, the nylon mesh material must be
cut so as not to lie over the bracket collar (Fig. 9).

(6) Complete the bracket installation following the

instructions provided with the rear view mirror adhe-
sive kit.

(7) Reinstall the rain sensor and the rear view

mirror onto the rain sensor bracket. (Refer to 8 -
ELECTRICAL/WIPERS/WASHERS/RAIN SENSOR -
INSTALLATION).

Fig. 7 Cut Nylon Mesh Fabric

1 - FABRIC
2 - DIAGONAL CUT

Fig. 8 Trim Nylon Mesh Fabric

1 - FABRIC
2 - BRACKET

Fig. 9 Rain Sensor Brackets

1 - COLLAR
2 - EARLY TYPE BRACKET
3 - LATE TYPE BRACKET

VA

WIPERS/WASHERS

8R - 13

(8) Reconnect the battery negative cable.

REMOVAL

WARNING: To avoid personal injury or death, on
vehicles equipped with airbags, disable the supple-
mental

restraint

system

before

attempting

any

steering wheel, steering column, airbag, seat belt
tensioner, or instrument panel component diagno-
sis or service. Disconnect and isolate the battery
negative (ground) cable, then wait two minutes for
the system capacitor to discharge before perform-
ing further diagnosis or service. This is the only
sure way to disable the supplemental restraint sys-
tem. Failure to take the proper precautions could
result in accidental airbag deployment.

(1) Disconnect and isolate the battery negative

cable.

(2) Unsnap the base covers from each other and

remove them from the rear view mirror arm at the
windshield (Fig. 10).

(3) Using a small thin-bladed screwdriver, gently

pry the retaining collar slightly upward while press-
ing the mirror arm downward parallel to the wind-
shield until the mirror arm unsnaps from the
bracket.

(4) Separate and remove the two halves of the

wire cover from the rain sensor pigtail wires.

(5) Loosen the screws securing both inner sun

visor hinges to the windshield header.

(6) Pull the headliner down from the windshield

header far enough to pull the rain sensor pigtail wire
connector out from under the headliner.

(7) Remove the anti-rattle felt from the wire con-

nector insulators.

(8) Disconnect the sensor pigtail wire connector

from the roof wire harness connector.

CAUTION: Do not touch the gel-like surface of the
rain sensor or the sensor function may be impaired
and the sensor rendered unusable.

(9) Remove the rain sensor from the center of the

bracket.

INSTALLATION

WARNING: To avoid personal injury or death, on
vehicles equipped with airbags, disable the supple-
mental

restraint

system

before

attempting

any

steering wheel, steering column, airbag, seat belt
tensioner, or instrument panel component diagno-
sis or service. Disconnect and isolate the battery
negative (ground) cable, then wait two minutes for
the system capacitor to discharge before perform-
ing further diagnosis or service. This is the only
sure way to disable the supplemental restraint sys-
tem. Failure to take the proper precautions could
result in accidental airbag deployment.

CAUTION: Do not touch the gel-like surface of the
rain sensor or the sensor function may be impaired
and the sensor rendered unusable.

(1) Position the rain sensor into the center of the

bracket on the windshield (Fig. 10).

(2) Reconnect the sensor pigtail wire connector to

the roof wire harness connector.

(3) Reinstall the anti-rattle felt over the wire con-

nector insulators.

(4) Pull the headliner down from the windshield

header far enough to tuck the rain sensor pigtail
wire connector under the headliner.

(5) Tighten the screws securing both inner sun

visor hinges to the windshield header.

(6) Align and install the two halves of the wire

cover over the rain sensor pigtail wires.

(7) Press the rear view mirror arm upward paral-

lel to the windshield until the mirror arm snaps onto
the bracket.

(8) Align and position the base covers to each

other and snap them over the rear view mirror arm
at the windshield.

(9) Reconnect the battery negative cable.

Fig. 10 Rain Sensor Remove/Install

1 - FELT
2 - CONNECTOR
3 - INNER VISOR HINGE (2)
4 - WIRE COVER
5 - BRACKET
6 - SENSOR
7 - RETAINING COLLAR
8 - BASE COVER
9 - MIRROR
10 - ARM

8R - 14

WIPERS/WASHERS

VA